text: /* cmdline.h: a reentrant version of getopt(). Written 2006 by Brian
   * Raiter. This code is in the public domain.
   */
  
  #ifndef	_cmdline_h_
  #define	_cmdline_h_
  
  /* The information specifying a single cmdline option.
   */
  typedef struct option {
      char const *name;		/* the option's long name, or "" if none */
      char	chname;		/* a single-char name, or zero if none */
      int		optval;		/* a unique value representing this option */
      int		arg;		/* 0 = no arg, 1 = arg req'd, 2 = optional */
  } option;
  
  /* Parse the given cmdline arguments. list is an array of option
   * structs, each entry specifying a valid option. The last struct in
   * the array must have name set to NULL. argc and argv give the
   * cmdline to parse. callback is the function to call for each option
   * and non-option found on the cmdline. data is a pointer that is
   * passed to each invocation of callback. The return value of callback
   * should be zero to continue processing the cmdline, or any other
   * value to abort. The return value of readoptions() is the value
   * returned from the last callback, or zero if no arguments were
   * found, or -1 if an error occurred.
   *
   * When readoptions() encounters a regular cmdline argument (i.e. a
   * non-option argument), callback() is invoked with opt equal to zero
   * and val pointing to the argument. When an option is found,
   * callback() is invoked with opt equal to the optval field in the
   * option struct corresponding to that option, and val points to the
   * option's paramter, or is NULL if the option does not take a
   * parameter. If readoptions() finds an option that does not appear in
   * the list of valid options, callback() is invoked with opt equal to
   * '?'. If readoptions() encounters an option that is missing its
   * required parameter, callback() is invoked with opt equal to ':'. If
   * readoptions() finds a parameter on a long option that does not
   * admit a parameter, callback() is invoked with opt equal to '='. In
   * each of these cases, val will point to the erroneous option
   * argument.
   */
  extern int readoptions(option const* list, int argc, char **argv,
  		       int (*callback)(int opt, char const *val, void *data),
  		       void *data);
  
  /* Parse the given file. list is an array of option structs, in the
   * same form as taken by readoptions(). fp is a pointer to an open
   * text file. callback is the function to call for each line found in
   * the configuration file. data is a pointer that is passed to each
   * invocation of callback. The return value of readcfgfile() is the
   * value returned from the last callback, or zero if no arguments were
   * found, or -1 if an error occurred while reading the file.
   *
   * The function will ignore lines that contain only whitespace, or
   * lines that begin with a hash sign. All other lines should be of the
   * form "OPTION=VALUE", where OPTION is one of the long options in
   * list. Whitespace around the equal sign is permitted. An option that
   * takes no arguments can either have a VALUE of 0 or 1, or omit the
   * "=VALUE" entirely. (A VALUE of 0 will behave the same as if the
   * line was not present.)
   */
  extern int readcfgfile(option const* list, FILE *fp,
  		       int (*callback)(int opt, char const *val, void *data),
  		       void *data);
  
  
  /* Create an argc-argv pair from a string containing a command line.
   * cmdline is the string to be parsed. argcp points to the variable to
   * receive the argc value, and argvp points to the variable to receive
   * the argv value. argvp can be NULL if the caller just wants to get
   * argc. Zero is returned on failure. This function allocates memory
   * on behalf of the caller. The memory is allocated as a single block,
   * so it is sufficient to simply free() the pointer returned through
   * argvp. Note that argv[0] will always be initialized to NULL; the
   * first argument will be stored in argv[1]. The string is parsed by
   * separating arguments on whitespace boundaries. Space within
   * substrings enclosed in single-quotes is ignored. A substring
   * enclosed in double-quotes is treated the same, except that the
   * backslash is recognized as an escape character within such a
   * substring. Enclosing quotes and escaping backslashes are not copied
   * into the argv values.
   */
  extern int makecmdline(char const *cmdline, int *argcp, char ***argvp);
  
  #endif
  