\chapter{Library support}
\label{chp:Library}

\section{Standard C libraries}
\label{sec:StandardCLibtraries}
\index{libraries!standard C}

This section describes how the standard C library is supported by
EiC. Note, any function, macro or type that is underlined is currently not
supported by EiC.

\subsection{assert.h}
\index{assert}
\label{sec:assert}

The header files \verb+<assert.h>+ defines the following macro:

\begin{Ventry2}{01234567890123456790}

\item[assert]
\index{assert}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <assert.h>
void assert(int expression);
\end{verbatim}
\end{production}

     If \T{expression} is false, a message is printed
     to \T{stderr} and abort is called to terminate execution.  However, EiC does not call
	abort. The source file and line
     number in the output message comes from the preprocessor macros \verb+__FILE__+ and
	\verb+__LINE__+.
	If \T{NDEBUG} is defined when \verb+<assert.h>+ is included, the assert macro is ignored.

\end{Ventry2}

\subsection{ctype.h}
\index{ctype}
\label{sec:ctype}

\begin{Ventry2}{comm-switch  }

\item[isdigit]
\index{isdigit}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <ctype.h>
int isdigit(int c);
\end{verbatim}
\end{production}

Returns 1 if \T{c} is in the set \verb+'0' - '9'+.
Otherwise it returns 0.

\item[isupper]
\index{isupper}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <ctype.h>
int isupper(int c);
\end{verbatim}
\end{production}

Returns 1 if \T{c} is in the set \verb+'A' - 'Z'+.  Otherwise
return it returns 0.

\item[islower]
\index{islower}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <ctype.h>
int islower(int c);
\end{verbatim}
\end{production}

Returns  1 if \T{c} is in the set \verb+'a' - 'z'+.  Otherwise
returns 0.

\item[isalpha]
\index{isalpha}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <ctype.h>
int isalpha(int c);
\end{verbatim}
\end{production}

Returns a 1 if \T{c} is in the set \verb+'A' - 'Z'+ or in \verb+'a' - 'z'+.
Otherwise returns 0.

\item[isprint]
\index{isprint}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <ctype.h>
int isprint(int c);
\end{verbatim}
\end{production}

Returns 1 if \T{c} is a printable character.  Otherwise returns 0.

\item[isalnum]
\index{isalnum}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <ctype.h>
int isalnum(int c);
\end{verbatim}
\end{production}

Returns 1 if \T{c} is in one of the sets \verb+'a' - 'z'+,
\verb+'A' - 'Z'+, or \verb+'0' - '9'+.  Otherwise returns 0.

\item[isspace]
\index{isspace}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <ctype.h>
int isspace(int c);
\end{verbatim}
\end{production}

Returns 1 if \T{c} is in the set \verb+' ', '\t', '\n', '\v', '\f', or '\r'+.
Otherwise returns  0.

\item[toupper]
\index{toupper}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <ctype.h>
int toupper(int c);
\end{verbatim}
\end{production}

If \T{c} is a lower case alphabetic character, \T{touppper} returns its upper
case equivalent, otherwise it returns \T{c}.

\item[tolower]
\index{tolower}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <ctype.h>
int tolower(int c);
\end{verbatim}
\end{production}

If \T{c} is an upper case alphabetic character, \T{tolower} returns its
lower case equivalent, otherwise it returns \T{c}.

\end{Ventry2}

\subsection{errno.h}
\index{header!errno.h}
\label{sec:errnoh}

The header \verb+<errno.h>+ contains manifest constants for error
codes. The variable \T{errno} is a modifiable {\it lvalue} that has
type \T{int}. It is set to zero on EiC startup, and it is used to
report various runtime errors; for example:

\begin{production}
\begin{verbatim}
#include <math.h>
#include <errno.h>
#include <assert.h>
int main(void)
{
    assert(errno == 0);
    sqrt(-3);
    assert(errno == EDOM);
}
\end{verbatim}
\end{production}

The \verb+<errno.h>+ files declares the following macros and object.

\begin{Ventry2}{01234567890123456789 }

\item[EDOM]
\index{EDOM}
\label{item:EDOM}
	Which stands for domain error. It occurs if an argument is
	outside the domain of a function; for example: \verb+sqrt(-2)+.

\item[ERANGE]
\index{ERANGE}
\label{item:ERANGE}
	Which stands for range error and is used for reporting various
	numerical overflow and underflow errors. It occurs if the
	result of a \T{math.h} function (see~\SecPage{mathh}) cannot
	be represented as a double.

\item[errno]
\index{errno}
\label{item:ERRNO}
	Is a modifiable {\it lvalue} with type \T{int} that may
	or may not be a real identifiable object.

\end{Ventry2}

\subsection{float.h}
\index{header!float.h}
\label{sec:floath}

In C, floating point values are represented in the normalised form:
\[
	x = s \times b^e \times \sum^{p}_{k=1}f_{k}\times b^{-k}, e_{\min}\leq e \leq e_{\max}
\]
where,
\begin{production}
\begin{tabular}{ll}
$s$ & sign ($\pm$1) \\
$b$ & is the base or radix, typically 2, 8, 10 or 16. \\
$e$ & the exponent, a value between a minimum $e_{\min}$ and a maximum $e_{\max}$. \\
$p$ & precision (the number of base-$b$ digits in the significand). \\
$f_k$ & the significant digits.
\end{tabular}
\end{production}

The header file \verb+<float.h>+ declares the following macros:

\begin{Ventry2}{01234567890123456789 }

\item[FLT\_RADIX]
\index{FLT\_RADIX}
\label{item:FLTRADIX}
	radix of exponent representing $b$.
\item[FLT\_ROUNDS]
\index{FLT\_ROUNDS}
\label{item:FLTROUNDS}
	Indicates the rounding mode for floats point values:\\
	-1, undetermined\\
	0  toward zero \\
	1 to the nearest  \\
	2 towards positive infinity \\
	3 towards negative infinity

\item[FLT\_DIG]
\index{FLT\_DIG}
\label{item:FLTDIG}
	number of digits of precision in a \T{float}
\item[FLT\_EPSILON]
\index{FLT\_EPSILON}
\label{item:FLTEPSILON}
     smallest number x such that 1.0 + x != 1.0

\item[FLT\_MANT\_DIG]
\index{FLT\_MANT\_DIG}
\label{item:FLTMANTDIG}
	the number of {\it base-b} digits in the floating-point significand.

\item[FLT\_MAX]
\index{FLT\_MAX}
\label{item:FLTMAX}
     maximum floating-point number
\item[FLT\_MAX\_10\_EXP]
\index{FLT\_MAX\_10\_EXP}
\label{item:FLTMAX10EXP}
     maximum $x$ such that $10^x$ is representable
\item[FLT\_MAX\_EXP]
\index{FLT\_MAX\_EXP}
\label{item:FLTMAXEXP}
	The maximum $n$ such that $\T{FLT\_RADIX}^n-1$ is representable

\item[FLT\_MIN]
\index{FLT\_MIN}
\label{item:FLTMIN}
     minimum normalised floating-point number
\item[FLT\_MIN\_10\_EXP]
\index{FLT\_MIN\_10\_EXP}
\label{item:FLTMIN10EXP}
	minimum $n$ such that $10^n$ is a normalised number.
\item[FLT\_MIN\_EXP]
\index{FLT\_MIN\_EXP}
\label{item:FLTMINEXP}
	minimum $n$ such that $b^{n-1}$ is a normalised number.

\item[DBL\_DIG]
\index{DBL\_DIG}
\label{item:DBLDIG}
	number of digits of precision in a \T{double}
\item[DBL\_EPSILON]
\index{DBL\_EPSILON}
\label{item:DBLEPSILON}
     smallest number x such that 1.0 + x != 1.0

\item[DBL\_MANT\_DIG]
\index{DBL\_MANT\_DIG}
\label{item:DBMANTDIG}
	the number of {\it base-b} digits in the floating-point significand.
\item[DBL\_MAX]
\index{DBL\_MAX}
\label{item:DBLMAX}
     maximum double floating-point number
\item[DBL\_MAX\_10\_EXP]
\index{DBL\_MAX\_10\_EXP}
\label{item:DBLMAX10EXP}
     maximum $x$ such that $10^x$ is representable
\item[DBL\_MAX\_EXP]
\index{DBL\_MAX\_EXP}
\label{item:DBLMAXEXP}
	The maximum $n$ such that $\T{FLT\_RADIX}^n-1$ is representable
\item[DBL\_MIN]
\index{DBL\_MIN}
\label{item:DBLMIN}
     minimum normalised double floating-point number
\item[DBL\_MIN\_10\_EXP]
\index{DBL\_MIN\_10\_EXP}
\label{item:DBMIN10EXP}
	minimum $n$ such that $10^n$ is a normalised number.
\item[DBL\_MIN\_EXP]
\index{DBL\_MIN\_EXP}
\label{item:DBMINEXP}
	minimum $n$ such that $b^{n-1}$ is a normalised number.

\end{Ventry2}

\subsection{limits.h}
\index{header!limits.h}
\label{sec:limitsh}

The header file \verb+<limits.h>+ declares the following macros:

\begin{Ventry2}{01234567890123456789 }

\item[CHAR\_BIT]
\index{CHAR\_BIT}
\label{item:CHARBIT}
     number of bits in a char
\item[CHAR\_MAX]
\index{CHAR\_MAX}
\label{item:CHARMAX}
     maximum value of char
\item[CHAR\_MIN]
\index{CHAR\_MIN}
\label{item:CHARMIN}
     minimum value of char
\item[INT\_MAX]
\index{INT\_MAX}
\label{item:INTMAX}
     maximum value of int
\item[INT\_MIN]
\index{INT\_MIN}
\label{item:INTMIN}
     minimum value of int
\item[LONG\_MAX]
\index{LONG\_MAX}
\label{item:LONGMAX}
     maximum value of long
\item[LONG\_MIN]
\index{LONG\_MIN}
\label{item:LONGMIN}
     minimum value of long
\item[SCHAR\_MAX]
\index{SCHAR\_MAX}
\label{item:SCHARMAX}
     maximum value of signed char
\item[SCHAR\_MIN]
\index{SCHAR\_MIN}
\label{item:SCHARMIN}
     minimum value of signed char
\item[SHRT\_MAX]
\index{SHRT\_MAX}
\label{item:SHRTMAX}
     maximum value of short
\item[SHRT\_MIN]
\index{SHRT\_MIN}
\label{item:SHRTMIN}
     minimum value of short
\item[UCHAR\_MAX]
\index{UCHAR\_MAX}
\label{item:UCHARMAX}
     maximum value of unsigned char
\item[UCHAR\_MIN]
\index{UCHAR\_MIN}
\label{item:UCHARMIN}
     minimum value of unsigned char
\item[UINT\_MAX]
\index{UINT\_MAX}
\label{item:UINTMAX}
     maximum value of unsigned int
\item[ULONG\_MAX]
\index{ULONG\_MAX}
\label{item:ULONGMAX}
     maximum value of unsigned long
\item[USHRT\_MAX]
\index{USHRT\_MAX}
\label{item:USHRTMAX}
     maximum value of unsigned short

\end{Ventry2}

\subsection{math.h}
\index{header!math.h}
\label{sec:mathh}

The header \verb+<math.h>+ declares the following macro:

\begin{Ventry2}{01234567890123456789 }

\item[HUGE\_VAL]
\index{HUGE\_VAL}
\label{item:HUGEVAL}
	A positive \T{double}. The largest representable floating point value.
	Not necessarily representable by a \T{float}.

\end{Ventry2}

The following functions are defined \verb+<math.h>+

\begin{Ventry2}{comm-switch  }

\item[atan]
\index{atan}
\label{item:atan}

\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <math.h>
double atan(double x);
\end{verbatim}
\end{production}

Returns the arc tangent of x.

\item[ceil]
\index{ceil}
\label{item:ceil}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <math.h>
double ceil(double x);
\end{verbatim}
\end{production}

Returns the smallest integer greater than or equal to x. The
returned value is a double.

\item[cos]
\index{cos}
\label{item:cos}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <math.h>
double cos(double x);
\end{verbatim}
\end{production}

Returns the cosine of x.

\item[cosh]
\index{cosh}
\label{item:cosh}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <math.h>
double cosh(double x);
\end{verbatim}
\end{production}

Returns the hyperbolic cosine of x.

\item[exp]
\index{exp}
\label{item:exp}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <math.h>
double exp(double x);
\end{verbatim}
\end{production}

Returns the exponential function of x.

\item[fabs]
\index{fabs}
\label{item:fabs}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <math.h>
double fabs(double x);
\end{verbatim}
\end{production}

Returns the absolute value of x. The value returned is a
double.

\item[floor]
\index{floor}
\label{item:floor}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <math.h>
double floor(double x);
\end{verbatim}
\end{production}

Returns the largest integer less than or equal to x. The
returned value is a double.

\item[sin]
\index{sin}
\label{item:sin}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <math.h>
double sin(double x);
\end{verbatim}
\end{production}

Returns the sine of x.

\item[sinh]
\index{sinh}
\label{item:sinh}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <math.h>
double sinh(double x);
\end{verbatim}
\end{production}

Returns the hyperbolic sine of x.

\item[sqrt]
\index{sqrt}
\label{item:sqrt}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <math.h>
double sqrt(double x);
\end{verbatim}
\end{production}

Returns the square root of x.

\item[tan]
\index{tan}
\label{item:tan}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <math.h>
double tan(double x);
\end{verbatim}
\end{production}

Returns the tangent of x.

\item[tanh]
\index{tanh}
\label{item:tanh}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <math.h>
double tanh(double x);
\end{verbatim}
\end{production}

Returns the hyperbolic tangent of x.

\item[log]
\index{log}
\label{item:log}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <math.h>
double log(double x);
\end{verbatim}
\end{production}

Returns the natural logarithm of x.

\item[log10]
\index{log10}
\label{item:log10}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <math.h>
double log10(double x);
\end{verbatim}
\end{production}

Returns the base 10 logarithm of x.

\item[pow]
\index{pow}
\label{item:pow}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <math.h>
double pow(double x, double y);
\end{verbatim}
\end{production}

Returns x raised to the yth power.

\item[atan2]
\index{atan2}
\label{item:atan2}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <math.h>
double atan2(double x, double y);
\end{verbatim}
\end{production}

Returns the arc tangent of \verb+y/x+.

\end{Ventry2}

\subsection{setjmp.h}
\index{header!setjmp.h}
\label{sec:setjmph}

The header \verb+<setjmp.h>+ declares the following macro and type:

\begin{Ventry2}{01234567890123456789 }

\item[jmp\_buf]
\index{jmp\_buf}
\label{item:jmpbuf}
     An array of type suitable for holding the information needed to restore a calling
environment.

\item[setjmp]
\label{item:setjmp}
\index{setjmp}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <setjmp.h>
int setjmp(jmp_buf env);
\end{verbatim}
\end{production}

     The \T{setjmp} macro save the calling environment in
     \T{env}. Zero returned from direct call; non-zero from subsequent
     call of \T{longjmp}.

\end{Ventry2}

The following macro function is defined in \verb+<setjmp.h>+:

\begin{Ventry2}{comm-switch  }

\item[longjmp]
\label{item:longjmp}
\index{longjmp}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <setjmp.h>
void longjmp(jmp_buf env, int val);
\end{verbatim}
\end{production}

     Restore state saved by most recent call to \T{setjmp} using
     information saved in \T{env}. Execution resumes as if \T{setjmp}
     just executed and returned non-zero value \T{val}.  Also,
     \verb+longjmp(env,0)+ is equivalent to \verb+longjmp(env,1)+. If
     the function containing \T{setjmp} has terminated before the
     \T{longjmp} call is made then EiC's behaviour will be undefined.

\end{Ventry2}

     An example usage of \T{setjmp} and \T{longjmp} is:

\begin{production}
\begin{verbatim}
#include <stdio.h>
#include <setjmp.h>

jmp_buf env;

void dojump() {longjmp(env,1);}

void dosetjmp()
{
    switch(setjmp(env)) {
       case 0: printf("setjmp return 0\n"); break;
       case 1: printf("setjmp return 1\n"); return;
       default: printf("error\n"); return;
    }
    dojump();
}

int main()
{
    dosetjmp();
    printf("exit main\n");
    return 0;
}
\end{verbatim}
\end{production}

Which should output:

\begin{production}
\begin{verbatim}
setjmp return 0
setjmp return 1
exit main
\end{verbatim}
\end{production}

\subsection{signal.h}
\index{header!signal.h}
\label{sec:signalh}

The header \verb+<signal.h>+ declares the following macros:

\begin{Ventry2}{01234567890123456789 }

\item[SIGABRT]
\index{SIGABRT}
\label{item:SIGABRT}
     abnormal termination
\item[SIGFPE]
\index{SIGFPE}
\label{item:SIGFPE}
     arithmetic error
\item[SIGILL]
\index{SIGILL}
\label{item:SIGILL}
     illegal function image
\item[SIGINT]
\index{SIGINT}
\label{item:SIGINT}
     interactive attention
\item[SIGSEGV]
\index{SIGSEGV}
\label{item:SIGSEGV}
	illegal storage access
\item[SIGTERM]
\index{SIGTERM}
\label{item:SIGTERM}
     termination request sent to program

\end{Ventry2}

The header \verb+<signal.h>+ defines the following macro functions, which can be used
to specify the action for the signal:

\begin{Ventry2}{01234567890123456789 }

\item[SIG\_DFL]
\index{SIG\_DFL}
\label{item:SIGDFL}
	 specifies the default action for the particular signal.
\item[SIG\_IGN]
\index{SIG\_IGN}
\label{item:SIGIGN} specifies that the signal should be ignored.

\end{Ventry2}

If a signal cannot honored its call, it returns \T{SIG\_ERR}.

\begin{Ventry2}{01234567890123456789 }

\item[SIG\_ERR]
\index{SIG\_ERR}
\label{item:SIGERR}
This macro is used as a return value to indicate an error.

\end{Ventry2}

EiC also supports POSIX.1 signals (see~\SecPage{signalhPosix}).

The following functions are defined in \verb+<signal.h>+:

\begin{Ventry2}{comm-switch  }

\item[signal]
\label{item:signal}
\index{signal}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <signal.h>
void (*signal(int sig, void (*handler)(int)))(int);
\end{verbatim}
\end{production}

     Install \T{handler} for subsequent signal \T{sig}. If \T{handler}
     is \T{SIG\_DFL}, implementation-defined default behaviour is
     used; if \T{handler} is \T{SIG\_IGN}, signal is ignored;
     otherwise function pointed to by handler is called with argument
     \T{sig}. signal returns the previous handler or \T{SIG\_ERR} on
     error.  When signal \T{sig} subsequently occurs, the signal is
     restored to its default behaviour and the \T{handler} is
     called. If the \T{handler} returns, execution resumes where the
     signal occurred. The initial state of the signals is
     implementation-defined.

     When you install a signal handler  within EiC you will most likely be overriding one of
EiC's own internal signal handling routines:

\begin{production}
\begin{verbatim}

EiC 1> #include <signal.h>
        	(void)
EiC 2> raise(SIGFPE);

EiC maths  exception, file ::EiC::, line 2
EiC::Reset Local Stack Pointer
EiC: error clean up entry pt 0,1,2,3,4,

\end{verbatim}
\end{production}

	EiC assigns handlers for the following signals: \T{SIGBUS,
SIGFPE, SIGILL, SIGINT, SIGSEGV, SIGUSR1}.  It does this to keep the
flow of an EiC interactive session going. That is, it prevents your
code from causing EiC to abort in an undignified manner. While, in
none-interactive mode it is no big deal if you override one of EiC's
internal signal handlers, since you are saying that you will be
handling that signal, but in an interactive session, things are
different. You load translation units (\SecPage{PhasesTranslation}),
execute them, and various translation units may have no
relationship to each other. Therefore, when you assign a new signal handler
you should keep track of the initial one and reset it when appropriate:

\begin{production}
\begin{verbatim}
EiC 1> #include <signal.h>
        (void)
EiC 2> void foo(int sig) { printf("my handle\n"); }
        (void)
EiC 3> void (*oldhandle)(int) = signal(SIGFPE,foo);
        (void)
EiC 4> raise(SIGFPE);
SIGFPE passed
        0
EiC 5> signal(SIGFPE,oldhandle); // reestablish old handle
        0x80babe8
EiC 6> raise(SIGFPE);

EiC maths  exception, file ::EiC::, line 6
EiC::Reset Local Stack Pointer
EiC: error clean up entry pt 0,1,2,3,4,
\end{verbatim}
\end{production}

\item[raise]
\label{item:raise}
\index{raise}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <signal.h>
int raise(int sig);
\end{verbatim}
\end{production}

     Send signal \T{sig} to the program. Non-zero returned if unsuccessful.

As an example program try \T{examples/sig1.c}

\begin{production}
\begin{verbatim}
#include <stdio.h>
#include <signal.h>
#include <unistd.h>
void tick(int i) { printf("tick\n"); return;}
void tock(int i) { printf("tock\n"); return;}
int main()
{
    int i = 0, cnt = 1;
    while(1) {
        signal(SIGINT,tick); // note you must reestablish the handler
        sleep(1);
        raise(SIGINT);

        signal(SIGINT,tock);
        sleep(1);
        raise(SIGINT);
        if(i++==cnt)
            break;
    }
    signal(SIGINT,SIG_DFL);  // reset
    return 0;
}
\end{verbatim}
\end{production}

Which should out put:
\begin{production}
\begin{verbatim}
%> eic examples/sig1.c
tick
tock
tick
tock
\end{verbatim}
\end{production}

\end{Ventry2}

\subsection{stdarg.h}
\index{header!stdarg.h}
\label{sec:stdargh}

Defines macros that support functions with
variable argument lists.

\begin{Ventry2}{comm-switch  }

\item[va\_list]
\label{item:valist}
\index{va\_list}

	A type used to hold the information needed by the macros defined
in \verb+<stdarg.h>+.

\item[va\_start]
\label{item:vastart}
\index{va\_start}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdarg.h>
void va_start(va_list ap, lastarg);
\end{verbatim}
\end{production}

     Initialisation macro to be called once, and before any unnamed
     argument is accessed. The argument \T{ap} must be declared as a
     local variable, and \T{lastarg} is the last named parameter in
     the controlling function's parameter list.

\item[va\_arg]
\label{item:vaarg}
\index{va\_arg}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdarg.h>
type va_arg(va_list ap, type);
\end{verbatim}
\end{production}

     Produce a value of the type (\T{type}) and corresponding to the
     next unnamed argument. It modifies the value of \T{ap}.

\item[va\_end]
\label{item:vaend}
\index{va\_end}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdarg.h>
void va_end(va_list ap);
\end{verbatim}
\end{production}

     Must be called once, generally after all arguments have been
processed, but definetly before function exit.

\end{Ventry2}

\subsection{stddef.h}
\index{header!stddef.h}
\label{sec:stddefh}

The header \verb+<stddef.h>+ declares the following macros and types:

\begin{Ventry2}{01234567890123456789 }

\item[ptrdiff\_t]
\index{ptrdiff\_t}
\label{item:ptrdifft}
	An implementation defined signed integral type, which
	represents the type of the result of subtracting two pointers.

\item[size\_t]
\index{size\_t}
\label{item:sizet}
	An unsigned integral type, which is the return type
	from the operator \T{sizeof}.

\item[NULL]
\index{NULL}
\label{item:NULL}
	Implementation defined null pointer constant.

\item[offsetof]
\index{offsetof}
\label{item:offsetof}

	\T{offsetof({\it type}, {\it member-designator})} \\
	Expands to type \T{size\_t}, representing the offset in bytes
	of the structure member {\it member-designator} from the start
	of the structure {\it type}.

\item[\underline{wchar\_t}]
\index{}
\label{item:}
	An integral type that can represent all values for any extended character
	in the set supported by \T{locales}.

\end{Ventry2}

\subsection{stdio.h}
\index{header!stdio.h}
\label{sec:stdioh}

\T{stdio.h} has the following types and macros defined:

\begin{Ventry2}{01234567890123456789}

\item[FILE]
\label{item:FILE}
\index{FILE}

     Type which records information necessary to control a stream.
\item[fpos\_t]
\label{item:fpost}
\index{fpos\_t}
	Variable used for specification of positions within an opened file.
\item[size\_t]
\index{size\_t}
	See \verb+<stddef.h>+ \SecPage{stddefh}
\item[stdin]
\label{item:stdin}
\index{stdin}
     Standard input stream. Automatically opened when a program begins
     execution.
\item[stdout]
\label{item:stdout}
\index{stdout}
     Standard output stream. Automatically opened when a program begins
     execution.
\item[stderr]
\label{item:stderr}
\index{stderr}
     Standard error stream. Automatically opened when a program begins
     execution.
\item[FILENAME\_MAX]
\label{item:FILENAMEMAX}
\index{FILENAME\_MAX}
     Maximum permissible length of a file name
\item[FOPEN\_MAX]
\label{item:FOPENMAX}
\index{FOPEN\_MAX}
     Maximum number of files which may be open simultaneously.
\item[TMP\_MAX]
\label{item:TMPMAX}
\index{TMP\_MAX}
     Maximum number of temporary files during program execution.
\item[NULL]
	See \verb+<stddef.h>+ \SecPage{stddefh}
\item[\_IOFBF]
\label{item:IOFBF}
\index{\_IOFBF}
\item[\_IOLBF]
\label{item:IOLBF}
\index{\_IOLBF}
\item[\_IONBF]
\label{item:IONBF}
\index{\_IONBF}
	Macros used for the third argument to function \T{setvbuf}.
\item[BUFSIZ]
\label{item:BUFSIZ}
\index{BUFSIZ}
	The default buffer size used by \T{setbuf}.
\item[EOF]
\label{item:EOF}
\index{EOF}
	Macro used to indicate the end-of-file.
\item[L\_tmpnam]
\label{item:Ltmpnam}
\index{L\_tmpnam}
	Macro that expands to an intergergral constant expression, which is the size for
	the array of characters allocated to the default name returned by function \T{tmpnam}.
\item[SEEK\_SET]
\label{item:SEEKSET}
\index{SEEK\_SET}
\item[SEEK\_CUR]
\label{item:SEEKCUR}
\index{SEEK\_CUR}
\item[SEEK\_END]
\label{item:SEEKEND}
\index{SEEK\_END}
	Macros values used by \T{fseek} to locate current file seek
position with respect to the beginning of the file, the current file
position, or the end of the file respectively.

\end{Ventry2}

The following functions are defined in \T{stdio.h}

\begin{Ventry2}{comm-switch  }

\item[fopen]
\label{item:fopen}
\index{fopen}

\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
FILE* fopen(const char* filename, const char* mode);
\end{verbatim}
\end{production}

     Opens file \T{filename} and returns a pointer to an opened
stream, or NULL on failure. The stream can be opened with \T{mode}:

\begin{production}
\begin{verbatim}
"a"    Append. The file is created if it does not exist.
"w"    Write. If the file exists, it is deleted first.
"r"    Read. The file must already exist.
"r+"   Read and write. The file must already exist.
"w+"   Read and write. If the file exists, it is deleted
       first.
"a+"   Read and append. The file is created if it does  not
       exist.
"ab"   Append binary. The file is created if it does not
       exist.
"rb"   Open binary file for reading.
"wb"   Write binary file. If the files exist, it gets truncated
       to  zero first.
"ab+" or "a+b"  Append binary update.
"rb+" or "r+b"  Read binary update.
"wb+" or "w+b"  Write binary update.
\end{verbatim}
\end{production}

\item[freopen]
\index{freopen}
\label{item:freopen}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
FILE* freopen(const char* filename,
              const char* mode,
              FILE* stream);
\end{verbatim}
\end{production}

     Opens file \T{filename} with the specified \T{mode} and associates with it the
     specified \T{stream}. Returns stream or \T{NULL} on error. Usually used to change
     files associated with \T{stdin}, \T{stdout}, \T{stderr}.

\item[fflush]
\index{fflush}
\label{item:fflush}
\T{Synopsis}

\begin{production}
\begin{verbatim}
#include <stdio.h>
int fflush(FILE* stream);
\end{verbatim}
\end{production}

     Flushes stream \T{stream}. Effect undefined for input
     \T{stream}. Returns \T{EOF} for write error, zero
     otherwise. \T{fflush(NULL)} flushes all output streams.

\item[fclose]
\index{fclose}
\label{item:fclose}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int fclose(FILE* stream);
\end{verbatim}
\end{production}

     Closes stream \T{stream} (after flushing, if output stream). Returns \T{EOF} on
     error, zero otherwise.

\item[remove]
\index{remove}
\label{item:remove}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int remove(const char* filename);
\end{verbatim}
\end{production}

     Removes file \T{filename}. Returns non-zero on failure.

\item[rename]
\index{rename}
\label{item:rename}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int rename(const char* oldname, const char* newname);
\end{verbatim}
\end{production}

     Changes name of file \T{oldname} to \T{newname}. Returns non-zero on failure.

\item[tmpfile]
\index{tmpfile}
\label{item:tmpfile}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
FILE* tmpfile();
\end{verbatim}
\end{production}

     Creates temporary file (mode "wb+") which will be removed when closed or
     on normal program termination. Returns stream or NULL on failure.

\item[tmpname]
\index{tmpname}
\label{item:tmpname}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
char* tmpname(char s[L_tmpnam]);
\end{verbatim}
\end{production}

     Assigns to \T{s} and returns unique name for temporary file.

\item[setvbuf]
\index{setvbuf}
\label{item:setvbuf}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int setvbuf(FILE* stream, char* buf, int mode, size_t size);
\end{verbatim}
\end{production}

     Controls buffering for stream \T{stream} and can only be used
	after the stream pointer by \T{stream} has been associated
	initially with an open file and before any read or write
	operations are performed. The argument \T{mode} determines how
	\T{stream} will be buffered such as \T{\_IOLB}, \T{\_IOFBF},
	\T{\_IONBF}.  If \T{buf} is non-NULL then setvbuf will assign
	it as the buffer for \T{stream} otherwise \T{setvbuf} will
	allocate one and the value at \T{size} will determine the size
	of the buffer.

	Returns zero on success or nonzero on error.

\item[setbuf]
\index{setbuf}
\label{item:setbuf}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
void setbuf(FILE* stream, char* buf);
\end{verbatim}
\end{production}

     Controls buffering for stream \T{stream}. See also
	\T{setvbuf}~\pageref{item:setvbuf}.

\item[fprintf]
\index{fprintf}
\label{item:fprintf}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int fprintf(FILE* stream, const char* format, ...);
\end{verbatim}
\end{production}

     Converts (with format \T{format}) and writes output to stream
     \T{stream}. Number of characters written [negative on error] is
     returned. Between % and format conversion character:

\begin{production}
\begin{verbatim}
Flags:
- ........ left adjust
+ ........ always sign
space .... outputs a space if the first character is not a
           sign.
0 ........ zero pad
# ........ Alternate form: for conversion character o,
           first digit will be zero, for [xX], prefix 0x
           or 0X to  non-zero, for [eEfgG], always decimal
           point, for [gG] trailing zeros not removed.
Width:
Period:
Precision:
  for conversion character s, maximum characters to be
  printed from the string, for [eEf], digits after decimal
  point, for [gG], significant digits, for an integer,
  minimum  number of digits to be printed.
Length modifier:
h ............. short or unsigned short
l ............. long or unsigned long
L ............. long double
Conversions:
d, i .......... int; signed decimal notation
o    .......... int; unsigned octal notation
x,X  .......... int; unsigned hexadecimal notation
u    .......... int; unsigned decimal notation
c    .......... int; single character
s    .......... char* ; outputs the character of a string
f    .......... double; [-]mmm.ddd
e,E  .......... double; [-]m.dddddde(+|-)xx
g,G  .......... double
p    .......... void*; print as pointer
n    .......... int*; number of chars written into arg
%    .......... print %
\end{verbatim}
\end{production}
Example Uses of of the format string in \T{fprintf}:

\begin{verbatim}
%3d     print in a 3 digit field, right justified
%3.0f   print no decimal point and no fraction
%3.1f   print 1 digit after the decimal point
%.1f    print 1 digit after the decimal point, any width
\end{verbatim}

Between the % and the conversion character there may be a minus sign,
to specify left adjustment of the field, and two digit strings
separated by a period.  The first string specifies minimum field
width, and the second string specifies the maximum number of chars
to be printed from the string.

\begin{verbatim}
:%10s:          :hello, world:
:%-10s:         :hello, world:
:%20s:          :        hello, world:
:%-20s:         :hello, world        :
:%20.10s:       :          hello, wor:
:%-20.10s:      :hello, wor          :
:%.10s:         :hello, wor:
\end{verbatim}

\item[printf]
\index{printf}
\label{item:printf}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int printf(const char* format, ...);
\end{verbatim}
\end{production}

     \T{printf(f, ...)} is equivalent to \T{fprintf(stdout, f, ...)}

\item[sprintf]
\index{sprintf}
\label{item:sprintf}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int sprintf(char* s, const char* format, ...);
\end{verbatim}
\end{production}

     Like \T{fprintf}, but output written into string \T{s}, which must be
     large enough to hold the output, rather than to a stream. Output
     is null terminated; that is, the null character.  Return length
     does not include the null terminating character.

\item[vfprintf]
\index{vfprintf}
\label{item:vfprintf}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int vfprintf(FILE* stream, const char* format, va_list arg);
\end{verbatim}
\end{production}

     Equivalent to \T{fprintf} except that the variable argument list
     is replaced by \T{arg}, which must have been initialised by the
     \T{va\_start} macro and may have been used in calls to
     \T{va\_arg}. See \verb+<stdarg.h>+

\item[vprintf]
\index{vprintf}
\label{item:vprintf}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int vprintf(const char* format, va_list arg);
\end{verbatim}
\end{production}

     Equivalent to \T{printf} except that the variable argument list is replaced by
     \T{arg}, which must have been initialised by the \T{va\_start} macro and may have
     been used in calls to \T{va\_arg}. See verb+<stdarg.h>+

\item[vsprintf]
\index{vsprintf}
\label{item:vsprintf}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int vsprintf(char* s, const char* format, va_list arg);
\end{verbatim}
\end{production}

     Equivalent to \T{sprintf} except that the variable argument list is replaced
     by \T{arg}, which must have been initialised by the \T{va\_start} macro and may
     have been used in calls to \T{va\_arg}. See \verb+<stdarg.h>+

\item[fscanf]
\index{fscanf}
\label{item:fscanf}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int fscanf(FILE* stream, const char* format, ...);
\end{verbatim}
\end{production}

     Performs formatted input conversion, reading from stream \T{stream} according
     to format \T{format}. The function returns when \T{format} is fully processed.
     Returns \T{EOF} if end-of-file or error occurs before any conversion;
     otherwise, the number of items converted and assigned. Each of the
     arguments following format must be a pointer. Format string may contain:

\footnotesize
\begin{verbatim}
   o Blanks, Tabs : ignored
   o ordinary characters : expected to match next non-white-space
   o % : Conversion specification, consisting of %, optional assignment
     suppression character *, optional number indicating maximum field
     width, optional [hlL] indicating width of target, conversion
     character.
Conversion characters:
d
     decimal integer; int* parameter required
i
     integer; int* parameter required; decimal, octal or hex
o
     octal integer; int* parameter required
u
     unsigned decimal integer; unsigned int* parameter required
x
     hexadecimal integer; int* parameter required
c
     characters; char* parameter required; up to width; no '\0'
     added; no skip
s
     string of non-white-space; char* parameter required; '\0' added
e,f,g
     floating-point number; float* parameter required
p
     pointer value; void* parameter required
n
     chars read so far; int* parameter required
[...]
     longest non-empty string from set; char* parameter required; '\0'
[^...]
     longest non-empty string not from set; char* parameter
     required; '\0'
%
          literal %; no assignment
\end{verbatim}
\normalsize

\item[scanf]
\index{scanf}
\label{item:scanf}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int scanf(const char* format, ...);
\end{verbatim}
\end{production}

     \T{scanf(f, ...)} is equivalent to \T{fscanf(stdin, f, ...)}

\item[sscanf]
\index{sscanf}
\label{item:sscanf}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int sscanf(char* s, const char* format, ...);
\end{verbatim}
\end{production}

     Like \T{fscanf}, but input read from string \T{s}.

\item[fgetc]
\index{fgetc}
\label{item:fgetc}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int fgetc(FILE* stream);
\end{verbatim}
\end{production}

     Returns next character from stream \T{stream} as an \T{unsigned}
     \T{char}, or \T{EOF} on end-of-file or error.

\item[fgets]
\index{fgets}
\label{item:fgets}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
char* fgets(char* s, int n, FILE* stream);
\end{verbatim}
\end{production}

     Reads at most the next \T{n}-1 characters from stream stream into \T{s}, stopping
     if a newline is encountered (after copying the newline to s). s is
     null terminated. Returns \T{s}, or \T{NULL} on end-of-file or error.

\item[fputc]
\index{fputc}
\label{item:fputc}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int fputc(int c, FILE* stream);
\end{verbatim}
\end{production}

     Writes \T{c}, converted to \T{unsigned char}, to stream \T{stream}. Returns the
     character written, or \T{EOF} on error.

\item[fputs]
\index{fputs}
\label{item:fputs}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
char* fputs(const char* s, FILE* stream);
\end{verbatim}
\end{production}

     Writes \T{s}, which need not contain \verb+'\n'+ on stream stream. Returns
     non-negative on success, \T{EOF} on error.

\item[getc]
\index{getc}
\label{item:getc}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int getc(FILE* stream);
\end{verbatim}
\end{production}

     Equivalent to \T{fgetc} except that it may be a macro.

\item[getchar]
\index{getchar}
\label{item:getchar}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int getchar();
\end{verbatim}
\end{production}

     Equivalent to \T{getc(stdin)}.

\item[gets]
\index{gets}
\label{item:gets}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
char* gets(char* s);
\end{verbatim}
\end{production}

     Reads next line from \T{stdin} into \T{s}. Replaces terminating newline with \verb+'\0'+.
     Returns \T{s}, or \T{NULL} on end-of-file or error.

\item[putc]
\index{putc}
\label{item:putc}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int putc(int c, FILE* stream);
\end{verbatim}
\end{production}

     Equivalent to \T{fputc} except that it may be a macro.

\item[putchar]
\index{putchar}
\label{item:putchar}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int putchar(int c);
\end{verbatim}
\end{production}

     \T{putchar(c)} is equivalent to \T{putc(c, stdout)}.

\item[puts]
\index{puts}
\label{item:puts}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int puts(const char* s);
\end{verbatim}
\end{production}

     Writes \T{s} and a newline to \T{stdout}. Returns non-negative on success, \T{EOF} on
     error.

\item[unget]
\index{unget}
\label{item:unget}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int unget(int c, FILE* stream);
\end{verbatim}
\end{production}

     Pushes \T{c} (which must not be EOF), converted to \T{unsigned
     char}, onto stream \T{stream} such that it will be returned by the
     next read. Only one character of pushback is guaranteed for a
     stream. Returns \T{c}, or \T{EOF} on error.

\item[fread]
\index{fread}
\label{item:fread}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
size_t fread(void* ptr,
             size_t size,
             size_t nobj,
             FILE* stream);
\end{verbatim}
\end{production}

     Reads at most \T{nobj} objects of size \T{size} from stream
     \T{stream} into \T{ptr}.  Returns the number of objects
     read. \T{feof} and \T{ferror} must be used to determine status.

\item[fwrite]
\index{fwrite}
\label{item:fwrite}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
size_t fwrite(const void* ptr,
              size_t size,
              size_t nobj,
              FILE* stream);
\end{verbatim}
\end{production}

     Writes to stream \T{stream}, \T{nobj} objects of size \T{size}
     from array \T{ptr}. Returns the number of objects written (which
     will be less than \T{nobj} on error).

\item[fseek]
\index{fseek}
\label{item:fseek}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int fseek(FILE* stream, long offset, int origin);
\end{verbatim}
\end{production}

     Sets file position for stream \T{stream}. For a binary file,
     position is set to \T{offset} characters from \T{origin}, which
     may be \T{SEEK\_SET} (beginning), \T{SEEK\_CUR} (current
     position) or \T{SEEK\_END} (end-of-file); for a text stream,
     \T{offset} must be zero or a value returned by \T{ftell} (in
     which case \T{origin} must be \T{SEEK\_SET}). Returns non-zero on
     error.

\item[ftell]
\index{ftell}
\label{item:ftell}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
long ftell(FILE* stream);
\end{verbatim}
\end{production}

     Returns current file position for stream \T{stream}, or -1L on error.

\item[rewind]
\index{rewind}
\label{item:rewind}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
void rewind(FILE* stream);
\end{verbatim}
\end{production}

     \T{rewind(stream)} is equivalent to \T{fseek(stream, 0L, SEEK\_SET)};

\item[fgetpos]
\index{fgetpos}
\label{item:fgetpos}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int fgetpos(FILE* stream, fpos_t* ptr);
\end{verbatim}
\end{production}

     Assigns current position in stream stream to \T{*ptr}. Type \verb+fpos_t+ is suitable
     for recording such values. Returns non-zero on error.
\item[fsetpos]
\index{fsetpos}
\label{item:fsetpos}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int fsetpos(FILE* stream, const fpos_t* ptr);
\end{verbatim}
\end{production}

     Sets current position of stream \T{stream} to \T{*ptr}. Returns non-zero on \T{error}.

\item[clearerr]
\index{clearerr}
\label{item:clearerr}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
void clearerr(FILE* stream);
\end{verbatim}
\end{production}

     Clears the end-of-file and error indicators for stream \T{stream}.

\item[feof]
\index{feof}
\label{item:feof}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int feof(FILE* stream);
\end{verbatim}
\end{production}

     Returns non-zero if end-of-file indicator for stream \T{stream} is set.

\item[ferror]
\index{ferror}
\label{item:ferror}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int ferror(FILE* stream);
\end{verbatim}
\end{production}

     Returns non-zero if error indicator for stream \T{stream} is set.

\item[perror]
\index{perror}
\label{item:perror}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
void perror(const char* s);
\end{verbatim}
\end{production}

     Prints \T{s} and implementation-defined error message corresponding to \T{errno}:
     \verb+fprintf(stderr, "%s: %s\n", s, "error message")+\\
     See \T{strerror}.

\end{Ventry2}

\subsection{stdlib.h}
\index{header!stdlib.h}
\label{sec:stdlibh}

The header file \verb+<stdlib.h>+ contains the following types and macros:
\begin{Ventry2}{012345678901234568}

\item[RAND\_MAX]    Integral constant, which is the maximum value returned from \T{rand}.
\index{RAND\_MAX}
\item[EXIT\_FAILURE]
\index{EXIT\_FAILURE}
\item[EXIT\_SUCCESS]  Macros defined for successful or unsuccessful program termination.
\index{EXIT\_SUCCESS}
\item[size\_t] See \verb+<stddef.h>+ \SecPage{stddefh}
\item[NULL] See \verb+<stddef.h>+ \SecPage{stddefh}
\item[div\_t]  A structure type as returned by the \T{div} function.
\index{div\_t}
\item[ldiv\_t] A structure type as returned by the \T{ldiv} function.
\index{ldiv\_t}
\item[\underline{wchar\_t}]
\end{Ventry2}

The following functions are defined in the header \verb+<stdlib.h>+:

\begin{Ventry2}{comm-switch  }

\item[atof]
\index{atof}
\label{item:atof}
\T{Synopsis}:

\begin{production}
\begin{verbatim}
#include <stdlib.h>
float atof(const char *s);
\end{verbatim}
\end{production}

Converts the string of ASCII characters, which represent a decimal
number to a float.  The string consists of optional leading spaces or
tabs, an optional plus or minus sign \verb!(+ or -)!
 followed by one or more decimal digits.  Returns the
value of the ASCII number string.  The string passed to
atof can contain a decimal point with digits to the right of
the decimal point.  It can also take the form of a floating
point constant.

\item[atoi]
\label{item:atoi}
\index{atoi}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
int atoi(const char* s);
\end{verbatim}
\end{production}

     Returns numerical value of \T{s}. Equivalent to
     \verb+(int)strtol(s,NULL,10)+.

\item[atol]
\label{item:atol}
\index{atol}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
long atol(const char* s);
\end{verbatim}
\end{production}

     Returns numerical value of s. Equivalent to \verb+strtol(s, NULL, 10)+.

\item[strtod]
\label{item:strtod}
\index{strtod}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
double strtod(const char* s, char** endp);
\end{verbatim}
\end{production}

     Converts prefix of \T{s} to double, ignoring leading white
     spaces. Stores a pointer to any unconverted suffix in *endp if
     endp is non-NULL. In the case of overflow, \T{HUGE\_VAL} is
     returned with the appropriate sign; for the case of underflow,
     zero is returned. In either case, errno is set to \T{ERANGE}.

\item[strtol]
\label{item:strtol}
\index{strtol}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
long strtol(const char* s, char** endp, int base);
\end{verbatim}
\end{production}

     Converts prefix of \T{s} to long, ignoring leading white
     spaces. Stores a pointer to any unconverted suffix in \T{*endp} if
     \T{endp} is non-NULL. If base between 2 and 36, that base used; if
     zero, leading 0X or 0x implies hexadecimal, a leading 0 implies
     octal, otherwise a decimal conversion is used. Leading 0X or 0x
     permitted for base 16. In the case of overflow, \T{LONG\_MAX} or
     for the case of underflow \T{LONG\_MIN} is returned and \T{errno}
     is set to ERANGE.

\item[strtoul]
\label{item:strtoul}
\index{strtoul}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
unsigned long strtoul(const char* s, char** endp, int base);
\end{verbatim}
\end{production}

     As for \T{strtol} except result is unsigned long and  in the case
	of overflow  \T{ULONG\_MAX} is returned.

\item[rand]
\label{item:rand}
\index{rand}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
int rand();
\end{verbatim}
\end{production}

     Returns pseudo-random number in range 0 to \T{RAND\_MAX}.

\item[srand]
\label{item:srand}
\index{srand}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
void srand(unsigned int seed);
\end{verbatim}
\end{production}

     Uses \T{seed} as \T{seed} for new sequence of pseudo-random
     numbers. The defautl initial  value for \T{seed} is 1.

\item[calloc]
\label{item:calloc}
\index{calloc}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
void* calloc(size_t nobj, size_t size);
\end{verbatim}
\end{production}

     Returns pointer to zero-initialised newly-allocated space for an
     array of \T{nobj} objects each of size \T{size}, or \T{NULL} if
     request cannot be satisfied.

\item[malloc]
\label{item:malloc}
\index{malloc}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
void* malloc(size_t size);
\end{verbatim}
\end{production}

     Returns pointer to uninitialised newly-allocated space for an
     object of size \T{size}, or \T{NULL} if request cannot be
     satisfied.

\item[realloc]
\label{item:realloc}
\index{realloc}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
void* realloc(void* p, size_t size);
\end{verbatim}
\end{production}

     Changes the size of the object to which \T{p} points to
     \T{size}. Contents unchanged to minimum of old and new sizes. If
     new size larger, new space is uninitialised. Returns pointer to
     the new space or, if request cannot be satisfied NULL leaving p
     unchanged.

\item[free]
\label{item:free}
\index{free}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
void free(void* p);
\end{verbatim}
\end{production}

     Deallocates space to which \T{p} points. If \T{p} is NULL there
     is no effect; otherwise it must be a pointer returned by \T{calloc},
     \T{malloc} or \T{realloc}.

\item[abort]
\label{item:abort}
\index{abort}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
void abort();
\end{verbatim}
\end{production}

     Causes program to terminate abnormally, as if by \T{raise(SIGABRT)}.

\T{item}[exit]
\label{item:exitC}
\index{exit}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
void exit(int status);
\end{verbatim}
\end{production}

     Causes normal program termination. Functions installed using
     \T{atexit} are called in reverse order of registration. Open
     files are flushed and open streams are closed and control is
     returned to environment. The value of \T{status} is returned to
     environment in an implementation-dependent manner. Zero indicates
     successful termination and the values \T{EXIT\_SUCCESS} and
     \T{EXIT\_FAILURE} may also be used.

\item[atexit]
\label{item:atexit}
\index{atexit}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
int atexit(void (*fcm)(void));
\end{verbatim}
\end{production}

     Registers \T{fcm} to be called, in reverse order, when the
	program terminates or via a call to T{exit}.  Returns zero on
	success else a non-zero value is returned.

\item[system]
\label{item:system}
\index{system}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
int system(const char* s);
\end{verbatim}
\end{production}

     Passes \T{s} to environment for execution. If \T{s} is \T{NULL},
     non-zero returned if command processor exists; return value is
     implementation-dependent if \T{s} is non-NULL.

\item[getenv]
\label{item:getenv}
\index{getenv}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
char* getenv(const char* name);
\end{verbatim}
\end{production}

     Returns (implementation-dependent) environment string associated with
     \T{name}, or \T{NULL} if no such string exists.

\item[puttenv]
\label{item:putenv}
\index{putenv}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
int putenv(const char* name);
\end{verbatim}
\end{production}

	Accepts a string in the form {\it name=value} and inserts it into the
	system environment list, and if needed replacing any previous definition.

     	Returns 0 on success or -1 on error. Errors: \T{ENOMEM} insufficient space to allocate
	new environment.

\item[besearch]
\label{item:bsearch}
\index{besearch}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
void* bsearch(const void* key,
              const void* base,
              size_t n,
              size_t size,
              int (*cmp)(const void* keyval,
                        const void* datum));
\end{verbatim}
\end{production}

     Searches \T{base[0]}...\T{base[n-1]} for item matching
     *\T{key}. Comparison function \T{cmp} must return negative if
     first argument is less than second, zero if equal and positive if
     greater. The n items of base must be in ascending order. Returns
     a pointer to the matching entry or \T{NULL} if not found.

\item[qsort]
\label{item:qsort}
\index{qsort}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
void qsort(void* base,
           size_t n,
           size_t size,
           int (*cmp)(const void *a1, const void * a2));
\end{verbatim}
\end{production}

     Arranges into ascending order the array
     \T{base[0]}...\T{base[n-1]} of objects of size size. Comparison
     function \T{cmp} must return negative if first argument is less than
     second, zero if equal and positive if greater.

\item[abs]
\label{item:abs}
\index{abs}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
int abs(int n);
\end{verbatim}
\end{production}

     Returns absolute value of \T{n}.

\item[labs]
\label{item:labs}
\index{labs}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
long labs(long n);
\end{verbatim}
\end{production}

     Returns absolute value of \T{n}.

\item[div]
\label{item:div}
\index{div}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
div_t div(int num, int denom);
\end{verbatim}
\end{production}

     Returns in fields \T{quot} and \T{rem} of structure of type
     \T{div\_t} the quotient and remainder of num/denom respectively.

\item[ldiv]
\label{item:ldiv}
\index{ldiv}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <stdlib.h>
ldiv_t ldiv(long num, long denom);
\end{verbatim}
\end{production}

     Returns in fields \T{quot} and \T{rem} of structure of type
     \T{ldiv\_t} the quotient and remainder of num/denom respectively.

\end{Ventry2}

\subsection{string.h}
\index{header!string.h}
\label{sec:stringh}

The header file \verb+<string.h>+ defines the following types and macros:
\begin{Ventry2}{01234567890123456790}
\item[size\_t] See \verb+<stddef.h>+ \SecPage{stddefh}
\item[NULL] See \verb+<stddef.h>+ \SecPage{stddefh}
\end{Ventry2}

The following functions are defined in \verb+<string.h>+:

\begin{Ventry2}{comm-switch  }

\item[strcpy]
\label{item:strcpy}
\index{strcpy}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
char* strcpy(char* s, const char* ct);
\end{verbatim}
\end{production}

     Copy \T{ct} to \T{s} including terminating null character. Returns
	a pointer to \T{s}.

\item[strncpy]
\label{item:strncpy}
\index{strncpy}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
char* strncpy(char* s, const char* ct, int n);
\end{verbatim}
\end{production}

     Copy at most \T{n} characters of \T{ct} to \T{s}. Pad with zeros
     if \T{ct} is of length less than \T{n}. Returns a pointer to \T{s}.

\item[strcat]
\label{item:strcat}
\index{strcat}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
char *strcat(char *s2, const char *s1);
\end{verbatim}
\end{production}

Concatenates the string pointed to by \T{s2} to the string pointed to by
\T{s1}.  The calling program must assure that \T{s1} has enough space for the
concatenation.

\item[strncat]
\label{item:strncat}
\index{strncat}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
char* strncat(char* s, const char* ct, int n);
\end{verbatim}
\end{production}

     Concatenate at most \T{n} characters of \T{ct} to
	\T{s}. Terminate \T{s} with the null character and returns a
	pointer to it.

\item[strcmp]
\label{item:strcmp}
\index{strcmp}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
int strcmp(const char* s1, const char* s2);
\end{verbatim}
\end{production}

  Compares two strings.  The comparison stops when a \T{null}
terminator is encountered in either of the two strings.
Returns a 0 if the two strings are identical, less than
zero if \T{s2} is greater than \T{s1}, and greater than zero if \T{s1}
is greater than \T{s2}.

\item[strdup]
\label{item:strdup}
\index{strdup}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
char * strdup(const char* s);
\end{verbatim}
\end{production}

      Returns a pointer to a new string which is a duplicate of the
       string s.  Memory for the new string is obtained with
       malloc, and can be freed with free.

\item[strncmp]
\label{item:strncmp}
\index{strncmp}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
int strncmp(const char* s1, const char* s2, int n);
\end{verbatim}
\end{production}

 Compares  two strings.  The comparison stops when a \T{null}
terminator is encountered in either of the two strings or
when n number of bytes are compared.  Returns a 0 if the
two strings are identical, less than zero if \T{s2} is greater
than \T{s1}, and greater than zero if \T{s1} is greater than \T{s2}.

\item[strchr]
\label{item:strchr}
\index{strchr}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
char* strchr(const char* s1, int c);
\end{verbatim}
\end{production}

     Return pointer to first occurrence of \T{c} in \T{s1}, or
     \T{NULL} if not found.

\item[strrchr]
\label{item:strrchr}
\index{strrchr}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
char* strrchr(const char* s1, int c);
\end{verbatim}
\end{production}

     Return pointer to last occurrence of \T{c} in \T{s1}, or \T{NULL} if not found.

\item[strspn]
\label{item:strspn}
\index{strspn}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
size_t strspn(const char* s1, const char* s2);
\end{verbatim}
\end{production}

     Return length of prefix of \T{s1} consisting entirely of characters in \T{s2}.

\item[strcspn]
\label{item:strcspn}
\index{strcspn}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
size_t strcspn(const char* s1, const char* s2);
\end{verbatim}
\end{production}

     Return length of prefix of \T{s1} consisting entirely of
     characters not in \T{s2}.

\item[strpbrk]
\label{item:strpbrk}
\index{strpbrk}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
char* strpbrk(const char* s1, const char* s2);
\end{verbatim}
\end{production}

     Return pointer to first occurrence within \T{s1} of any character of \T{s2}, or
     \T{NULL} if not found.

\item[strstr]
\label{item:strstr}
\index{strstr}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
char* strstr(const char* s1, const char* s2);
\end{verbatim}
\end{production}

     Return pointer to first occurrence of \T{s2} in \T{s1}, or
     \T{NULL} if not found.

\item[strlen]
\label{item:strlen}
\index{strlen}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
size_t strlen(const char* s1);
\end{verbatim}
\end{production}

     Return length of \T{s1}.

\item[strerror]
\label{item:strerror}
\index{strerror}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
char* strerror(int n);
\end{verbatim}
\end{production}

     Return pointer to implementation-defined string corresponding with error
     \T{n}.

\item[strtok]
\label{item:strtok}
\index{strtok}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
char* strtok(char* s, const char* ct);
\end{verbatim}
\end{production}

     A sequence of calls to \T{strtok} returns tokens from \T{s}
     delimted by a character in \T{ct}. A non-NULL \T{s} indicates the
     first call in a sequence. Also,\T{ct} may differ on each
     call. Returns \T{NULL} when no such token found.

\item[memcpy]
\label{item:memcpy}
\index{memcpy}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
void* memcpy(void* dest, const void* src, int n);
\end{verbatim}
\end{production}

     Copy \T{n} characters from \T{src} to \T{dest}. Return
     \T{dest}. Does not work correctly if objects overlap.

\item[memmove]
\label{item:memmove}
\index{memmove}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
void* memmove(void* dest, const void* src, int n);
\end{verbatim}
\end{production}

     Copy \T{n} characters from \T{src} to \T{dest}. Return
     \T{dest}. Works correctly even if objects overlap.

\item[memcmp]
\label{item:memcmp}
\index{memcmp}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
int memcmp(const void* s1, const void* s2, int n);
\end{verbatim}
\end{production}

     Compare first \T{n} characters of \T{s1} with \T{s2}. Return
     negative if \T{s1} < \T{s2}, zero if \T{s1} == \T{s2}, positive
     if \T{s1} > \T{s2}.

\item[memchr]
\label{item:memchr}
\index{memchr}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
void* memchr(const char* s1, int c, int n);
\end{verbatim}
\end{production}

     Return pointer to first occurrence of \T{c} in the first \T{n} characters
     of \T{s1}, or \T{NULL} if not found.

\item[memset]
\label{item:memset}
\index{memset}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <string.h>
void* memset(char* s, int c, int n);
\end{verbatim}
\end{production}

     Replace each of the first \T{n} characters of \T{s} by \T{c}. Return \T{s}.

\end{Ventry2}

\subsection{time.h}
\index{header!time.h}
\label{sec:timeh}

The header \verb+<time.h>+ declares the following macros and types:

\begin{Ventry2}{01234567890123456789 }

\item[clock\_t]
\index{clock\_t}
\label{item:clockt}

An arithmetic type representing time.

\item[time\_t]
\index{time\_t}
\label{item:timet}

     An arithmetic type representing time.

\item[CLOCKS\_PER\_SEC]
\index{CLOCKS\_PER\_SEC}
\label{item:CLOCKSPERSEC}

     The number of \T{clock\_t} units per second.

\item[struct tm]
\index{struct tm}
\label{item:struct tm}  Represents the components of calendar time:
\begin{verbatim}
     int tm_sec; /* seconds after the minute */
     int tm_min; /* minutes after the hour */
     int tm_hour; /* hours since midnight */
     int tm_mday; /* day of the month */
     int tm_mon; /* months since January */
     int tm_year; /* years since 1900 */
     int tm_wday; /* days since Sunday */
     int tm_yday; /* days since January 1 */
     int tm_isdst; /* Daylight Saving Time flag */
\end{verbatim}

The value of \T{tm\_isdst} is positive if Daylight saving time is in effect, zero if
          not in effect, negative if information unavailable.

\end{Ventry2}

The following functions are defined in \verb+<time.h>+:

\begin{Ventry2}{012345670123456}

\item[clock]
\label{item:clock}
\index{clock}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <time.h>
clock_t clock(void);
\end{verbatim}
\end{production}

     Returns processor time used by program or -1 if not available.
\item[time]
\label{item:time}
\index{time}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <time.h>
time_t time(time_t* tp);
\end{verbatim}
\end{production}

     Returns current calendar time or -1 if not available. If \T{tp} is non-NULL,
     return value is also assigned to *\T{tp}.
\item[difftime]
\label{item:difftime}
\index{difftime}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <time.h>
double difftime(time_t time2, time_t time1);
\end{verbatim}
\end{production}

     Returns the difference is seconds between \T{time2} and \T{time1}.
\item[mktime]
\label{item:mktime}
\index{mktime}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <time.h>
time_t mktime(struct tm* tp);
\end{verbatim}
\end{production}

     Returns the local time corresponding to *\T{tp}, or -1 if it cannot be
     represented.

\item[asctime]
\label{item:asctime}
\index{asctime}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <time.h>
char* asctime(const struct tm* tp);
\end{verbatim}
\end{production}

     Returns the given time as a string of the form:
     \verb+Sun Jan 3 14:14:13 1988\n\0+
\item[ctime]
\label{item:ctime}
\index{ctime}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <time.h>
char* ctime(const time_t* tp);
\end{verbatim}
\end{production}

     Converts the given calendar time, \T{tp}, to a local time and
     returns the equivalent string. Equivalent to:
     asctime(localtime(tp))

\item[gmtime]
\label{item:gmtime}
\index{gmtime}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <time.h>
struct tm* gmtime(const time_t* tp);
\end{verbatim}
\end{production}

     Returns the given calendar time converted into Coordinated Universal Time,
     or \T{NULL} if not available.

\item[localtime]
\label{item:localtime}
\index{localtime}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <time.h>
struct tm* localtime(const time_t* tp);
\end{verbatim}
\end{production}

     Returns calendar time *\T{tp} converted into local time.

\item[strftime]
\label{item:strftime}
\index{strftime}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <time.h>
size_t strftime(char* s,
                size_t smax,
                const char* fmt,
                const struct tm* tp);
\end{verbatim}
\end{production}

     Formats *\T{tp} into s according to \T{fmt}.

\item[Notes]

   Local time may differ from calendar time, for example because of time
     zone.

\end{Ventry2}

\section{POSIX.1 library support}
\label{sec:Posix.1Library}
\index{libraries!POSIX.1 support}

Here is EiC's current implementation of the POSIX.1 library. It is by
no means complete, but rather a strict subset. For those interested,
the POSIX.1 environment is more formally presented by
\cite{zlotnick91} or \cite{stevens92}.

The test macro \T{\_POSIX\_SOURCE} is used and as documented in the IEEE
POSIX.1 standard, where the programmer is required to define the
\T{\_POSIX\_SOURCE} feature test macro to obtain the \T{POSIX.1} namespace and
\T{POSIX.1} functionality.

This macro can be defined, at compile time \T{(-D\_POSIX\_SOURCE)} or
by using \T{\#define} directives in the source files before any
\T{\#include} directives:

\begin{production}
\begin{verbatim}
#define  _POSIX_SOURCE
#include <stdio.h>
#include <signal.h>
\end{verbatim}
\end{production}

It is only needed for those header shared between \T{POSIX.1} and
\T{ISO-C}, when the \T{POSIX.1} features are to be made visible
(header files that are underlined are currently not supported):

\footnotesize
\begin{center}
\label{tb:ISO-POSIX-headers}
\begin{tabular}{|r|l|r|l|}
\hline
ISO-C & POSIX.1 & IS0-C & POSIX.1\\
\hline

\T{assert.h}     &                 & \T{stdio.h}  & \T{\underline{stdio.h}} \\
\T{ctype.hr}     &                 & \T{stdlib.h} & \\
                 & \T{dirent.h}    & \T{string.h} & \\
\T{errno.h}      & \T{errno.h}     &              & \T{sys/stat.h} \\
                 & \T{fcntl.h}     &              & \T{\underline{sys/times.h}}  \\
\T{float.h}      &                 &              & \T{\underline{sys/utsname.h}}\\
                 & \T{\underline{grp.h}}       &              & \T{\underline{sys/wait.h}} \\
\T{iso646.h}     &                 &              & \T{termios.h}   \\
\T{limits.h}     & \T{limits.h}    & \T{time.h}   &  \T{\underline{time.h}}\\
\T{\underline{locale.h}}     &                 &              & \T{unistd.h}\\
\T{math.h}       &                 &              &\T{\underline{utime.h}}\\
\T{setjmp.h}     & \T{\underline{setjmp.h}}    & \T{\underline{wchar.h}}  &\\
\T{signal.h}     & \T{signal.h}    & \T{\underline{wctype.h}} &\\
\T{stdarg.h}     &                 &              & \\
\T{stddef.h}     &                 &              & \\
\hline
\end{tabular}
\end{center}
\normalsize

\subsection{dirent.h}
\index{header!dirent.h}
\label{sec:direnth}

The EiC header file \verb+<dirent.h>+ contains objects, types and
functions for reading and opening directories. To make or remove
a directory see section \SecPage{unistdh}. Also, while anyone with the
appropriate access permissions may read a directory, only the kernel
can write to a directory. Then \verb+<dirent.h>+ defines the following
type and structure:

\begin{Ventry2}{01234567890123456790}

\item[DIR]
\label{item:DIR}
\index{DIR}
	A directory stream is represented by the type \T{DIR}, which
	is similar to the \verb+<stdio.h>+ type \T{FILE}
	(page~\pageref{item:FILE}).

\item[struct dirent]
\label{item:struct dirent}
\index{struct dirent}
	While the the dirent structure is implementation dependent, it
	will contain at least:

\begin{production}
\begin{verbatim}
ino_t d_ino;  /* inode number of entry */
char d_name[NAME_SIZE + 1]; /* name (null-terminated) */
\end{verbatim}
\end{production}

Note the size of \T{d\_name} is also implementation dependent.  The
\T{dirent struct} specifies the structure type that is  used
to hold information about individual directory entries, such as
files etc.

\end{Ventry2}

The following functions are defined in \verb+<dirent.h>+:
\begin{Ventry2}{comm-switch  }

\item[closedir]
\label{item:closedir}
\index{closedir}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <sys/types.h>
#include <dirent.h>
int closedir(DIR *dirp);
\end{verbatim}
\end{production}

Closes the directory stream associated with \T{dirp}.
Returns  0  on success, or -1 on error and sets \T{errno} to
\T{EBADF}.

\item[opendir]
\index{opendir}
\label{item:opendir}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <sys/types.h>
#include <dirent.h>
DIR *opendir(const char *dirname);
\end{verbatim}
\end{production}

Opens the directory stream associated with the directory \T{dirname},
and returns a pointer to the opened stream.  The directory will be opened such
that, the stream pointer is positioned at the first entry in the
directory. Returns a pointer to the directory on success, else
\T{NULL} on error and will set
\T{errno} to one of: \T{EACESS}, \T{EMFILE}, \T{ENOENT}, \T{ENFILE},
\T{ENOMEM} or \T{ENOTDIR}.

\item[readdir]
\index{readdir}
\label{item:readdir}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <sys/types.h>
#include <dirent.h>
struct dirent *readdir(DIR *dirp);
\end{verbatim}
\end{production}

Reads the next dirent structure from the stream \T{dirp}.  Returns a
pointer to the associated \T{struct dirent}, else \T{NULL} if
the end-of-file mark has been reached or on an error,  and  in which case
it sets \T{errno} to \T{EBADF}.

\item[rewinddir]
\index{rewinddir}
\label{item:rewinddir}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <sys/types.h>
#include <dirent.h>
void rewinddir(DIR *dirp);
\end{verbatim}
\end{production}

Rewinds or resets the directory stream \T{dirp} back to the
beginning. No error codes used.

\end{Ventry2}

\subsection{errno.h}
\index{header!errno.h}
\label{sec:erronhPosix}

The header file \verb+<errno.h>+ has already been discussed with
respect to the ISO C library specifications (see~\SecPage{errnoh}). Here
its POSIX.1 additions are report.

The EiC header file \verb+<errno.h>+ defines the following extra
macros:

\begin{Ventry2}{01234567890123456789 }
\item[E2BIG]
\label{item:E2BIG}
\index{E2BIG}
	Argument list too long.
\item[EACCES]
\label{item:EACCES}
\index{EACCES}
	Permission denied.
\item[EAGAIN]
\label{item:EAGAIN}
\index{EAGAIN}
	Device or resource unavailable; try again later.
\item[EBADF]
\label{item:EBADF}
\index{EBADF}
	Bad file descriptor.
\item[EBUSY]
\label{item:EBUSY}
\index{EBUSY}
	Device or resource busy.
\item[ECHILD]
\label{item:ECHILD}
\index{ECHILD}
	No child processes.
\item[EDEADLK]
\label{item:DEADLK}
\index{ECHILD}
	Resource deadlock would result.
\item[EEXIST]
\label{item:EEXIST}
\index{EEXIST}
	File exists.
\item[EFAULT]
\label{item:EFAULT}
\index{EFAULT}
	Bad address.
\item[EFBIG]
\label{item:EFBIG}
\index{EFBIG}
	File too large.
\item[EINTR]
\label{item:EINTR}
\index{EINTR}
	Function interrupted system call.
\item[EINVAL]
\label{item:EINVAL}
\index{EINVAL}
	Invalid argument.
\item[EIO]
\label{item:EIO}
\index{EIO}
	I/O error.
\item[EISDIR]
\label{item:EISDIR}
\index{EISDIR}
	Is a directory.
\item[EMFILE]
\label{item:EMFILE}
\index{EMFILE}
	Too many open files.
\item[EMLINK]
\label{item:EMLINK}
\index{EMLINK}
	Too many links.
\item[ENAMETOOLONG]
\label{item:ENAMETOOLONG}
\index{ENAMETOOLONG}
	File name too long.
\item[ENFILE]
\label{item:ENFILE}
\index{ENFILE}
	File table overflow because of too many open files.
\item[ENODEV]
\label{item:ENODEV}
\index{ENODEV}
	No such device.
\item[ENOENT]
\label{item:ENOENT}
\index{ENOENT}
	No such file or directory.
\item[ENOEXEC]
\label{item:ENOEXEC}
\index{ENOEXEC}
	Executable format error, because file is not executable.
\item[ENOLCK]
\label{item:ENOLCK}
\index{ENOLCK}
	No record locks available.
\item[ENOMEM]
\label{item:ENOMEM}
\index{ENOMEM}
	Out of memory.
\item[ENOSPC]
\label{item:ENOSPC}
\index{ENOSPC}
	No space left on device.
\item[ENOSYS]
\label{item:ENOSYS}
\index{ENOSYS}
	Function not implemented or supported
\item[ENOTDIR]
\label{item:ENOTDIR}
\index{ENOTDIR}
	Not a directory.
\item[ENOTEMPTY]
\label{item:ENOTEMPTY}
\index{ENOTEMPTY}
	Directory not empty.
\item[ENOTTY]
\label{item:ENOTTY}
\index{ENOTTY}
	Not a typewriter or inappropriate I/O control operation.
\item[ENXIO]
\label{item:ENXIO}
\index{ENXIO}
	No such device or address.
\item[EPERM]
\label{item:EPERM}
\index{EPERM}
	Operation not permitte
\item[EPIPE]
\label{item:EPIPE}
\index{EPIPE}
	Broken pipe.
\item[EROFS]
\label{item:EROFS}
\index{EROFS}
	Read-only file system.
\item[ESPIPE]
\label{item:ESPIPE}
\index{ESPIPE}
	Illegal seek operation.
\item[ESRCH]
\label{item:ESRCH}
\index{ESRCH}
	No such process.
\item[EXDEV]
\label{item:EXDEV}
\index{EXDEV}
	Cross-device link; invalid link.

\end{Ventry2}

\subsection{fcntl.h}
\index{header!fcntl.h}
\label{sec:fcntlh}

The EiC header file \verb+<fcntl.h>+ defines the following macros:

\begin{Ventry2}{01234567890123456790}

\item[O\_APPEND]
\label{item:OAPPEND}
\index{O\_APPEND}
	If on, set offset to end-of-file before each write.
\item[O\_CREAT]
\label{item:OCREAT}
\index{O\_CREAT}
	If file does not exist, the the file is created
	and with file attribute according to the value
	of {\it mode}. If files does exist, then this
	flag has no effect.

\item[O\_EXCL]
\label{item:OEXCL}
\index{O\_EXCL}
	Fail if file exists and if \T{O\_CREAT} is also specified.
	Otherwise, create the file.

\item[O\_NOCTTY]
\label{item:ONOCTTY}
\index{O\_NOCTTY}
	Not used with regular files.

\item[O\_NONBLOCK]
\label{item:ONONBLOCK}
\index{O\_NONBLOCK}
	Not used with regular files.
\item[O\_RDONLY]
\label{item:ORDONLY}
\index{O\_RDONLY}
	Open for read only.
\item[O\_RDWR]
\label{item:ORDWR}
\index{O\_RDWR}

	Open for read and write.
\item[O\_TRUNC]
\label{item:OTRUNC}
\index{O\_TRUNC}
	If the file exists, its length will be truncated to zero.
\item[O\_WRONLY]
\label{item:OWRONLY}
\index{O\_WRONLY}
	Open for write only.

\item[O\_NDELAY]
\label{item:ONDELAY}
\index{O\_NDELAY}
	For compatibility with System V.3.

\item[O\_BINARY]
\label{item:OBINARY}
\index{O\_BINARY}
	Open file in binary mode. Added for DOS compatibility.
\item[O\_TEXT]
\label{item:OTEXT}
\index{O\_TEXT}
	Open file in text mode. Added for DOS compatibility.

\end{Ventry2}

The following functions are defined in \verb+<fcntl.h>+:
\begin{Ventry2}{comm-switch  }

\item[creat]
\label{item:creat}
\index{creat}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <sys/types.h>
#include <sys/stats.h>
#include <fcntl.h>
int creat(const char *path,  mode_t mode);
\end{verbatim}
\end{production}

Creates a new file or rewrites an existing one for writing,  as
specified by \T{path}. Its access is specified by \T{mode},
which maybe one or a bitwise combination of:
\T{S\_IS[UG]ID}, \T{S\_ISVTX}, \T{S\_I[RWX](GRP|USR|OTH)}.
It returns a nonnegative file descriptor if
successful, else it returns -1 and sets \T{errno} to one of:
\T{EACCES}, \T{EEXIST}, \T{EINTR}, \T{EISDIR}, \T{EMFILE}, \T{ENAMETOOLONG},
\T{ENFILE}, \T{ENOENT}, \T{ENOSPS}, \T{ENOTODIR}, or \T{EROFS}.

\item[open]
\label{item:open}
\index{open}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <sys/types.h>
#include <sys/stats.h>
#include <fcntl.h>
int open(const char *path, int access, ... /* mode_t mode */);
\end{verbatim}
\end{production}

Create or open the file specified by \T{path}, with access defined by
\T{access}, which maybe one or a bitwise combination of:
\T{O\_APPEND}, \T{O\_CREAT}, \T{O\_EXCL}, \T{O\_NONBLOCK},
\T{O\_NOCTTY},  \T{O\_RDONLY}, \T{O\_RDWR} or \T{O\_WRONLY}.
The extra argument \T{mode} is used when creating a file with the
access flag \T{O\_CREAT} specified. The \T{mode} maybe one or a bitwise
combination of
\T{S\_IS[UG]ID}, \T{S\_ISVTX}, \T{S\_I[RWX](GRP|USR|OTH)}. \T{Open}
returns a nonnegative file descriptor if successful, else it returns
-1 and sets \T{errno} to one of:
\T{EACCES}, \T{EEXIST}, \T{EINTR}, \T{EISDIR}, \T{EMFILE}, \T{ENAMETOOLONG},
\T{ENFILE}, \T{ENOENT}, \T{ENOSPS}, \T{ENOTODIR}, T{ENXIO} or \T{EROFS}.

\item[fcntl]
\label{item:fcntl}
\index{fcntl function}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
int fcntl(int filedes, int cmd, ..., /* optional int arg */);
\end{verbatim}
\end{production}

The properties of a file can be changed via the \T{fcntl} function.
It is used for the following five purposes:
\begin{enumerate}
\item Makes arg be a copy of fd, closing  fd  first  if
                necessary, when \T{cmd} = \T{ F\_DUPFD}.
\item Read or set file discriptor flags,  \T{cmd} = \T{F\_GETFD} or \T{F\_SETFD}.
\item Read or set a file's status flags , \T{cmd} = \T{F\_GETFL} or \T{F\_SETFL}.
\item Read or set the  process  ID  (or  process group) of the owner of a socket,
        \T{cmd} = \T{F\_GETOWN} or \T{F\_SETOWN}.
\item Read or set  record locks, \T{cmd} = \T{F\_GETL},
 \T{F\_SETLK} or \T{SETLKW}.
\end{enumerate}

All commands return -1 on error otherwise the return value depends on
the input command: \T{F\_DUPFD}, a new descriptor; \T{F\_GETFD}, the
value of the flag \T{F\_GETFL}  value of flags and \T{F\_GETOWN}
a positive or negative process \T{ID}.

On error, sets \T{errno} to one of: \T{EACCESS}, \T{EAGAIN}, \T{EDEADLK}.

\end{Ventry2}

\subsection{limits.h}
\index{header!limits.h}
\label{sec:limitshPosix}

The header \verb+<limits.h>+ declares the following POSIX.I macros:

\begin{Ventry2}{01234567890123456789 }

\item[ARG\_MAX]
\index{ARG\_MAX}
\label{item:ARGMAX}
	maximum length of argument to the `exec' function
\item[CHILD\_MAX]
\index{CHILD\_MAX}
\label{item:CHILDMAX}
	maximum number of simultaneous processes per real user ID at any one time
\item[LINK\_MAX]
\index{LINK\_MAX}
\label{item:LINKMAX}
	number of links a file may have
\item[MAX\_CANON]
\index{MAX\_CANON}
\label{item:MAXCANON}
	size of the canonical input queue
\item[MAX\_INPUT]
\index{MAX\_INPUT}
\label{item:MAXINPUT}
	size of the type-ahead buffer
\item[NAME\_MAX]
\index{NAME\_MAX}
\label{item:NAMEMAX}
	maximum number of bytes in a file name, not including null termination.
\item[NGROUPS\_MAX]
\index{NGROUPS\_MAX}
\label{item:NGROUPSMAX}
	maximum number of supplementary group IDs that one process can have.
\item[OPEN\_MAX]
\index{OPEN\_MAX}
\label{item:OPENMAX}
	number of files that a single process can have open simultaneously
\item[PIPE\_BUF]
\index{PIPE\_BUF}
\label{item:PIPEBUF}
	maximum number of bytes written atomically to a pipe
\item[SSIZE\_MAX]
\index{SSIZE\_MAX}
\label{item:SSIZEMAX}
	largest value for object of type ssize\_t
\item[TZNAME\_MAX]
\index{TZNAME\_MAX}
\label{item:TZNAMEMAX}
	maximum bumber of bytes for the a time zone name.
\item[\_POSIX\_ARG\_MAX]
\index{\_POSIX\_ARG\_MAX}
\label{item:POSIXARGMAX}
	Maximum length of arguments to `execve', including environment.
\item[\_POSIX\_CHILD\_MAX]
\index{\_POSIX\_CHILD\_MAX}
\label{item:POSIXCHILDMAX}
	Maximum simultaneous processes per real user ID.
\item[\_POSIX\_LINK\_MAX]
\index{\_POSIX\_LINK\_MAX}
\label{item:POSIXLINKMAX}
	Maximum link count of a file.
\item[\_POSIX\_MAX\_CANON]
\index{\_POSIX\_MAX\_CANON}
\label{item:POSIXMAXCANON}
	Number of bytes in a terminal canonical input queue.
\item[\_POSIX\_MAX\_INPUT]
\index{\_POSIX\_MAX\_INPUT}
\label{item:POSIXMAXINPUT}
	Number of bytes for which space will be available in a terminal input queue.
\item[\_POSIX\_NAME\_MAX]
\index{\_POSIX\_NAME\_MAX}
\label{item:POSIXNAMEMAX}
	Number of bytes in a filename.
\item[\_POSIX\_NGROUPS\_MAX]
\index{\_POSIX\_NGROUPS\_MAX}
\label{item:POSIXNGROUPSMAX}
	Number of simultaneous supplementary group IDs per process.
\item[\_POSIX\_OPEN\_MAX]
\index{\_POSIX\_OPEN\_MAX}
\label{item:POSIXOPENMAX}
	Number of files one process can have open at once.
\item[\_POSIX\_PATH\_MAX]
\index{\_POSIX\_PATH\_MAX}
\label{item:POSIXPATHMAX}
	Number of bytes in a pathname.
\item[\_POSIX\_PIPE\_BUF]
\index{\_POSIX\_PIPE\_BUF}
\label{item:POSIXPIPEBUF}
	Number of bytes than can be written atomically to a pipe.
\item[\_POSIX\_SSIZE\_MAX]
\index{\_POSIX\_SSIZE\_MAX}
\label{item:POSIXSSIZEMAX}
	Largest value of a `ssize\_t'.
\item[\_POSIX\_STREAM\_MAX]
\index{\_POSIX\_STREAM\_MAX}
\label{item:POSIXSTREAMMAX}
	Number of streams a process can have open at once.
\item[\_POSIX\_TZNAME\_MAX]
\index{\_POSIX\_TZNAME\_MAX}
\label{item:POSIXTZNAMEMAX}
	Maximum length of a timezone name (element of `tzname').
\item[\_POSIX\_QLIMIT]
\index{\_POSIX\_QLIMIT}
\label{item:POSIXQLIMIT}
	Maximum number of connections that can be queued on a socket.
\item[\_POSIX\_HIWAT]
\index{\_POSIX\_HIWAT}
\label{item:POSIXHIWAT}
	Maximum number of bytes that can be buffered on a socket for send  or receive.
\item[\_POSIX\_UIO\_MAXIOV]
\index{\_POSIX\_UIO\_MAXIOV}
\label{item:POSIXUIOMAXIOV}
	Maximum number of elements in an `iovec' array.
\item[\_POSIX\_TTY\_NAME\_MAX]
\index{\_POSIX\_TTY\_NAME\_MAX}
\label{item:POSIXTTYNAMEMAX}
	Maximum number of characters in a tty name.
\item[\_POSIX\_LOGIN\_NAME\_MAX]
\index{\_POSIX\_LOGIN\_NAME\_MAX}
\label{item:POSIXLOGINNAMEMAX}
	Maximum length of login name

\end{Ventry2}

\subsection{signal.h}
\index{header!signal.h}
\label{sec:signalhPosix}

The header \verb+<signal.h>+ declares the following POSIX.I macros:

\begin{Ventry2}{01234567890123456789 }

\item[SIGALRM]
\index{SIGALRM}
\label{item:SIGALRM}
	 Alarm clock.

\item[SIGCHLD]
\index{SIGCHLD}
\label{item:SIGCHLD}
	 Child process terminated or stopped.

\item[SIGHUP]
\index{SIGHUP}
\label{item:SIGHUP}
	 Hangup.

\item[SIGKILL]
\index{SIGKILL}
\label{item:SIGKILL}
	 Kill (cannot be caught or ignored).

\item[SIGPIPE]
\index{SIGPIPE}
\label{item:SIGPIPE}
	 Write on a pipe with no one to read it.
\item[SIGQUIT]
\index{SIGQUIT}
\label{item:SIGQUIT}
	 Terminal quit signal.

\item[SIGSTOP]
\index{SIGSTOP}
\label{item:SIGSTOP}
	 Stop executing (cannot be caught or ignored).
\item[SIGTSTP]
\index{SIGTSTP}
\label{item:SIGTSTP}
	 Terminal stop signal.

\item[SIGTTIN]
\index{SIGTTIN}
\label{item:SIGTTIN}
	 Background process attempting read.
\item[SIGTTOU]
\index{SIGTTOU}
\label{item:SIGTTOU}
	 Background process attempting write.

\item[SIGUSR1]
\index{SIGUSR1}
\label{item:SIGUSR1}
	 User-defined signal 1.
\item[SIGUSR2]
\index{SIGUSR2}
\label{item:SIGUSR2}
	 User-defined signal 2.

\end{Ventry2}

\subsection{sys/stat.h}
\index{header!sys/stat.h}
\label{sec:systath}

The EiC header file \verb+<sys/stats.h>+ defines symbolic constants
that are used when specifying the \T{mode\_t} access of files.  It
defines the following macros and one structure specifier:

\begin{Ventry2}{01234567890123456790}

\item[S\_IRGRP]
\label{item:SIRGRP}
\index{S\_IRGRP}
Group read permission.

\item[S\_IROTH]
\label{item:SIROTH}
\index{S\_IROTH}
Other read permission.

\item[S\_IRUSR]
\label{item:SIRUSR}
\index{S\_IRUSR}

Owner read permission. This is identical to the
\T{S\_IREAD}\index{S\_IREAD} used by DOS.

\item[S\_IRWXG]
\label{item:SIRWXG}
\index{S\_IRWXG}
Group read, write and execute permission.\\
\verb+S_IRWXG = S_IRGRP | S_IWGRP | SI_XGRP+

\item[S\_IRWXO]
\label{item:SIRWXO}
\index{S\_IRWXO}
Other read, write and  execute permission.\\
\verb+S_IRWXO = S_IROTH | S_IWOTH | S_IXOTH+

\item[S\_IRWXU]
\label{item:SIRWXU}
\index{S\_IRWXU}
Owner read, write and execute permission.\\
\verb+S_IRWXU = S_IRUSR | S_IWUSR | S_IXUSR+

\item[S\_ISBLK]
\label{item:SISBLK}
\index{S\_ISBLK}

Is block special file.

\item[S\_ISCHR]
\label{item:SISCHR}
\index{S\_ISCHR}

Is character special file.

\item[S\_ISDIR]
\label{item:SISDIR}
\index{S\_ISDIR}

Is directory.

\item[S\_ISFIFO]
\label{item:SISFIFO}
\index{S\_ISFIFO}
Is pipe or FIFO.

\item[S\_ISGID]
\label{item:SISGID}
\index{S\_ISGID}
set group id on execution

\item[S\_ISREG]
\label{item:SISREG}
\index{S\_ISREG}
set user id on execution

\item[S\_IWGRP]
\label{item:SIWGRP}
\index{S\_IWGRP}
Group write permission.

\item[S\_IWOTH]
\label{item:SIWOTH}
\index{S\_IWOTH}
Other write permission.

\item[S\_IWUSR]
\label{item:SIWUSR}
\index{S\_IWUSR}

Owner write permission. This is identical to
\T{S\_IWRITE}\index{S\_IWRITE} used by DOS.

\item[S\_IXGRP]
\label{item:SIXGRP}
\index{S\_IXGRP}
Group execute permission.

\item[S\_IXOTH]
\label{item:SIXOTH}
\index{S\_IXOTH}
Other execute permission.

\item[S\_IXUSR]
\label{item:SIXUSR}
\index{S\_IXUSR}
Owner execute permission.

\item[struct stat]
\label{item:structstat}
\index{struct stat}

A file status attributes are easily collected into a structure as
specified by \T{struct stat}, which has at least the following members:

\begin{verbatim}
mode_t  st_mode;    /* File mode */
ino_t   st_ino;     /* File serial number */
dev_t   st_dev;     /* File system device number */
nlink_t st_nlink;   /* Number of links */
uid_t   st_uid;     /* User ID of the file's owner */
gid_t   st_gid;     /* Group ID of the file's group */
off_t   st_size;    /* File size in bytes */
time_t  st_atime;   /* Time of last access */
time_t  st_mtime;   /* Time of last data modification */
time_t  st_ctime;   /* Time of last file status change */

/* ... */           /* other possible members */
\end{verbatim}

\end{Ventry2}

The following functions are defined in \verb+<sys/stat.h>+:
\begin{Ventry2}{comm-switch  }

\item[chmod]
\label{item:chmod}
\index{chmod}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <sys/types.h>
#include <sys/stat.h>
int chmod(const char * path, mode_t mode);
\end{verbatim}
\end{production}

Change access permission of the file specified by \T{path} to
\T{mode}, which maybe one or a bitwise combination of
\T{S\_IS[UG]ID}, \T{S\_ISVTX}, \T{S\_I[RWX](GRP|USR|OTH)}.
Returns zero on success or -1 on error and sets
\T{errno} to one of: \T{EACCESS}, \T{ENAMETOOLONG},
\T{ENOTDIR}, \T{ENOENT}, \T{EPERM} OR \T{EROFS}.

\item[fstat]
\label{item:fstat}
\index{fstat}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <sys/types.h>
#include <sys/stat.h>
int fstat(int filedes, struct stat *buf)
\end{verbatim}
\end{production}

Gets the open file or directory information associate with
\T{filedes}. It stores the information in the \T{stat} structure,
pointed to by \T{buf}. It returns zero on success,  else -1 on error and
sets \T{errno} to \T{EBADF}.

\item[mkdir]
\label{item:mkdir}
\index{mkdir}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <sys/types.h>
#include <sys/stat.h>
int mkdir(const char *path, mode_t mode)
\end{verbatim}
\end{production}

Creates a directory from the given path with access specified by
\T{mode}, which maybe one or a bitwise combination of
\T{S\_IS[UG]ID}, \T{S\_ISVTX}, \T{S\_I[RWX](GRP|USR|OTH)}.
Returns 0 on success, else -1 on error and then sets \T{errno} to one of:
\T{EACCESS}, \T{ENAMETOOLONG},
\T{ENOENT} or \T{ENOTDIR}.

\item[mkfifo]
\label{item:mkfifo}
\index{mkfifo}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <sys/types.h>
#include <sys/stat.h>
int mkfifo(const char * path, mode_t mode)
\end{verbatim}
\end{production}

Creates a FIFO name pipe with access specified by \T{mode},
which maybe one or a bitwise combination of
\T{S\_IS[UG]ID}, \T{S\_ISVTX}, \T{S\_I[RWX](GRP|USR|OTH)}.
Returns 0 on success, else -1 on error and sets
\T{errno} to one of: \T{EACCESS}, \T{EEXIST}, \T{ENAMETOOLONG},
\T{ENOENT}, \T{ENOSPC}, \T{ENOTDIR} or \T{EROFS}.

\item[stat]
\label{item:stat}
\index{stat}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <sys/types.h>
#include <sys/stat.h>
int stat(const char *file_name, struct stat *buf)
\end{verbatim}
\end{production}

The same as \T{fstat} above, but is applied to a file name rather than
an already opened file. Returns 0 on success, else -1 on error and sets
\T{errno} to one of: \T{EACCESS},
\T{ENAMETOOLONG}, \T{ENOENT} or \T{ENOTDIR}.

\item[umask]
\label{item:umask}
\index{umask}
\T{Synopsis}:
\begin{production}
\begin{verbatim}
#include <sys/types.h>
#include <sys/stat.h>
mode_t umask(mode_t cmask)
\end{verbatim}
\end{production}

Sets the file mode creation mask for the calling process to \T{cmask}.
Returns the previous creation mask. No error codes used.

\end{Ventry2}

\subsection{sys/types.h}
\index{header!sys/types.h}
\label{sec:systypesh}

The EiC header file \verb+<sys/types.h>+ defines the following object
types.

\begin{Ventry2}{01234567890123456790}

\item[dev\_t]
\label{item:devt}
\index{dev\_t}
Device number (major and minor).

\item[gid\_t]
\label{item:gidt}
\index{gid\_t}
Group ID.

\item[ino\_t]
\label{item:inot}
\index{ino\_t}
Numeric i-node value.

\item[mode\_t]
\label{item:modet}
\index{mode\_t}
	File type and creation mode.

\item[nlink\_t]
\label{item:nlinkt}
\index{nlink\_t}
	Number of links associated with a directory.

\item[off\_t]
\label{item:offt}
\index{off\_t}
	For recording file offset position and file sizes.

\item[pid\_t]
\label{item:pidt}
\index{pid\_t}
	Process ID number and process group ID>

\item[size\_t]
\index{size\_t}
	See section \SecPage{stddefh}

\item[ssize\_t]
\label{item:ssizet}
\index{ssize\_t}
	POSIX byte count.

\item[uid\_t]
\label{item:uidt}
\index{uid\_t}
	User IDs.

\end{Ventry2}

\subsection{unistd.h}
\index{header!unistd.h}
\label{sec:unistdh}

The EiC header file \verb+<unistd.h>+ defines the following macros:

\begin{Ventry2}{01234567890123456790}

\item[F\_OK]
\label{item:FOK}
\index{F\_OK}
	Does file exist.
\item[W\_OK]
\label{item:WOK}
\index{W\_OK}
	Writable by caller.
\item[R\_OK]
\label{item:ROK}
\index{R\_OK}
	Readable by caller.
\item[X\_OK]
\label{item:XOK}
\index{X\_OK}
	Executable by caller.
\item[STDIN\_FILENO]
\label{item:STDINFILENO}
\index{STDIN\_FILENO}
	Standard input.
\item[STDOUT\_FILENO]
\label{item:STDOUTFILENO}
\index{STDOUT\_FILENO}
	Standard output.
\item[STDERR\_FILENO]
\label{item:STDERRFILENO}
\index{STDERR\_FILENO}
Standard error output.

\end{Ventry2}

The following functions are presently implemented from
\verb+<unistd.h>+ by EiC:

\begin{Ventry2}{comm-switch  }

\item[access]
\label{item:access}
\index{access}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <unistd.h>
int access(const char * path, int mode);
\end{verbatim}
\end{production}

   Checks the file pointed to by \T{path} for accessibily according to
   \T{mode}, using the real user ID in place of the effective user ID
   and the real group ID in place of the effective group ID. This
   allows a setuid process to verify that the user running it would
   have had permission to access this file.  The \T{mode} can be
   \T{F\_OK}, \T{R\_OK}, \T{W\_OK}, or \T{X\_OK}. Returns zero on
success or -1 on failure and sets \T{errno} to one of:
     EACCES, ENAMETOOLONG, ENOENT, or EROFS.

\item[alarm]
\label{item:alarm}
\index{alarm}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <unistd.h>
unsigned int alarm(unsigned int seconds);
\end{verbatim}
\end{production}

\T{alarm} arranges to have a \T{SIGALRM} delivered to the process for the signal
\T{SIGALRM} after the specified number of seconds have elapsed. If \T{seconds} is zero
then no new alarm is schededuled. In all cases the any previous \T{alarm}s are cancelled and
\T{return}s the number of seconds remaining  until  any  scheduled alarm was due to be delivered.
\T{Return}s zero if there is no previously scheduled alarm.

\item[chdir]
\label{item:chdir}
\index{chdir}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <unistd.h>
int chdir(const char * pathname);
\end{verbatim}
\end{production}

\T{chdir} changes the current working directory to the one specified in \T{pathname}.
Returns on success, 0 and on error returns -1 and it will set \T{errno} to one of: \T{EFAULT}
 \T{ENAMETOOLONG}, \T{ENOENT}, \T{ENOMEM}, \T{ENOTDIR}, \T{EACCES}, \T{ELOOP}, \T{EIO}, \T{EBADF} or \T{EACCES}

\item[close]
\label{item:close}
\index{close}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <unistd.h>
int close(int handle);
\end{verbatim}
\end{production}

Closes the file associated with \T{handle}, which may have been
obtained from \T{creat}, \T{open}, \T{dup}, or \T{dup2}.
Returns 0 on success, else -1 on error and sets \T{errno}
to one of: \T{EBADF} or \T{EINTR}.

\item[dup]
\label{item:dup}
\index{dup}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <unistd.h>
int dup(int filedes);
\end{verbatim}
\end{production}

Duplicates the file handle \T{filedes}. The duplicated handle will
have the same access mode, the same file pointer and same open file or
device as \T{filedes}. Returns the duplicated file handle, else -1 on
error and sets \T{errno} to one of: \T{EBADF} or \T{EMFILE}.

\item[dup2]
\label{item:dup2}
\index{dup2}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <unistd.h>
int dup2(int oldfiledes, int newfiledes);
\end{verbatim}
\end{production}

Duplicates an old file handle, \T{oldfiledes} onto an existing new
file handle, \T{newfiledes}. The duplicated handle will have the same
access mode, the same file pointer and same open file or device as the
old handle.  If the file associated with the new file handle is
already opened, it will be first closed. Returns 0 on success, else -1
on error and sets \T{errno} to one of \T{EBADF} or \T{EMFILE}.

\item[fork]
\label{item:fork}
\index{fork}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <sys/types.h>
#include <unistd.h>
pid_t fork(void);
\end{verbatim}
\end{production}

Creates a child process, which is a copy of the parent. The child gets
a copy of the parent's data space, heap and stack. While \T{fork}
is called once, it will return twice: once to the parent and once to the
child. It returns 0 to the child and returns the process \T{ID} of the
child to the parent. Both the child and parent continue executing from
the place in the program directly after the call. However, there is no
guarantee which process will commence first. On error, it returns -1
and sets \T{errno} to one of: \T{EAGAIN} or \T{ENOMEM}.

\item[getcwd]
\label{item:getcwd}
\index{getcwd}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <unistd.h>
char *getcwd(char *buf, size_t sz);
\end{verbatim}
\end{production}

The \T{getcwd} function gets the current working directory's absolute
path and copies it into the character array \T{buf}, and the length of
\T{buf} is specified by \T{sz}. Returns on success \T{buf}, or
\T{NULL} on error.

\item[getpid]
\label{item:getpid}
\index{getpid}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <sys/types.h>
#include <unistd.h>
int getpid(void);
\end{verbatim}
\end{production}

Returns the group ID of the calling process.  No error
indicated or \T{errno} designators.

\item[link]
\label{item:link}
\index{link}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <unistd.h>
int link(const char *oldpath, const char *newpath);
\end{verbatim}
\end{production}

Creates a link to an existing file or directory specified
by\T{oldpath}, and give it the name \T{newpath}. It is an error if the
newpath already exists. Note, only a superuser process can create a
link to a directory.  Returns 0 on success, else -1 on error and sets
\T{errno} to one of: \T{EINVAL}, \T{EPERM} or \T{ESRCH}.

\item[lseek]
\label{item:lseek}
\index{lseek}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <sys/types.h>
#include <unistd.h>
off_t lseek(int filedes, off_t offset, int whence);
\end{verbatim}
\end{production}

Set the file descriptor's, \T{filedes}, pointer to the new position
specified by \T{offset}, which will be measured relative to
\T{whence}. \T{whence} can be on of:
\T{SEEK\_SET}, \T{SEEK\_END} or \T{SEEK\_CUR}. Returns on success the
resulting position in number of bytes from the beginning of the file,
else it returns -1 and sets \T{errno} to one of: \T{EBADF}, \T{EINVAL}
or \T{ESPIPE}. Note, \verb+lseek(filedes,0,SEEK_CUR)+ will return
the current file pointer location.

\item[pause]
\label{item:pause}
\index{pause}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <unistd.h>
int pause(void);
\end{verbatim}
\end{production}

Causes the program or calling unit to sleep until a signal is received.
\T{Return}s  -1.

\item[pipe]
\label{item:pipe}
\index{pipe}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <unistd.h>
int pipe(int filedes[2]);
\end{verbatim}
\end{production}

Creates a pipe, with read and write file descriptors stored in
filedes[0] and filedes[1] respectively. The output filedes[0] is the
input into file filedes[1]. A call to \T{pipe} is often accompanied by
a \T{fork}, of which the parent process will close the read end of the
pipe, while the child process will close the write end.  Returns 0 on
success, else -1 on error and sets
\T{errno} to one of: \T{EMFILE} or \T{ENFILE}.

\item[read]
\label{item:read}
\index{read}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <unistd.h>
ssize_t read(int filedes, char *buf, size_t count);
\end{verbatim}
\end{production}

Attempts to read \T{count} bytes from \T{filedes} and will place
them in \T{buf}. One success, returns the number of bytes read,
on \T{end-of-file} zero, otherwise -1 and sets \T{errno} to one of:
\T{EACCESS}, \T{EAGAIN}, \T{EBADF}, \T{EINTR}, \T{EISDIR}, or
\T{EFAULT}.

\item[rmdir]
\label{item:rmdir}
\index{rmdir}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <unistd.h>
int rmdir(const char * path);
\end{verbatim}
\end{production}

Removes the directory specified by \T{path}, which must be empty.
Returns zero on success, else -1 on error and
\T{errno} will be set to one of: \T{EBUSY}, \T{EFAULT},
\T{ENAMETOOLONG}, \T{ENOENT}, \T{ENOMEM}, \T{ENOTDIR},
 \T{ENOTEMPTY}, \T{EPERM } or \T{EROFS}.

\item[sleep]
\label{item:sleep}
\index{sleep}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <unistd.h>
unsigned int sleep(unsigned int sec);
\end{verbatim}
\end{production}

Puts the current process to sleep for  \T{sec} seconds.
or until a signal arrives which is not ignored. Returns
the amount of time not slept. No error codes used.

\item[unlink]
\label{item:unlink}
\index{unlink}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <unistd.h>
int unlink(const char *fname);
\end{verbatim}
\end{production}

Removes the link, \T{fname} from the filesystem. If it is the last
link to the that name and no other process has the file opened, then
the file space will also be freed. If there are no other links and any
process still has the file opened then the file space will remain in
existence until the last file descriptor referring to it is
closed. Returns zero on success, else -1 and
\T{errno} is set to one of: \T{EACCES}, \T{EFAULT}, \T{EISDIR},
\T{ENAMETOOLONG}, \T{ENOENT}, \T{ENOMEM}, \T{ENOTDIR},  \T{EPERM }, or \T{EROFS}.

\item[usleep]
\label{item:usleep}
\index{usleep}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <unistd.h>
void usleep(unsigned long usec);
\end{verbatim}
\end{production}

The \T{usleep} function when called waits \T{usec} microseconds before
returning to its caller.  Its accuracy depends on the time needed to
actually process the call, but as the value of \T{usec} increase so should its
accuracy. 1sec=$10^6$usec.

\item[write]
\label{item:write}
\index{write}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <unistd.h>
ssize_t write(int filedes, const char *buf, size_t count);
\end{verbatim}
\end{production}

Writes up to \T{count} bytes to file descriptor \T{filedes} from from
\T{buf}. Returns the number of bytes written, zero on end-of-file or
otherwise -1 and \T{errno} will be set to one of: \T{EAGAIN}, \T{EBADF},
\T{EFAULT}, \T{EINTR}, \T{EINVAL}, \T{ENOSPC} or \T{EPIPE}.

\end{Ventry2}

\section{Implementation library support}
\label{sec:ImplementationLibrary}
\index{libraries!implementation support}

In this section, those functions that are not part of ISO C or the POSIX.1
standard are presented. These functions will typically be found
on most UNIX system.

\subsection{stdio.h}
\index{header!stdio.h}
\label{sec:stdiohImplementation}

The EiC header file \verb+<stdio.h>+ defines the following
extra functions:

\begin{Ventry2}{01234567890123456790}

\item[pclose]
\label{item:pclose}
\index{pclose}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
int pclose( FILE *stream);
\end{verbatim}
\end{production}

\item[popen]
\label{item:popen}
\index{popen}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <stdio.h>
FILE *popen( const char *command, const char *type);
\end{verbatim}
\end{production}

\end{Ventry2}

\subsection{dirent.h}
\index{header!dirent.h}
\label{sec:direnthImplementation}

The EiC header file \verb+<dirent.h>+ defines these extra functions:

\begin{Ventry2}{01234567890123456790}

\item[seekdir]
\label{item:seekdir}
\index{seekdir}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <dirent.h>
void seekdir(DIR *dir, off_t offset);
\end{verbatim}
\end{production}

\item[telldir]
\label{item:telldir}
\index{telldir}
\T{Synopsis}
\begin{production}
\begin{verbatim}
#include <dirent.h>
off_t telldir(DIR *dir);
\end{verbatim}
\end{production}

\end{Ventry2}