text: sighold, sigignore, sigpause, sigrelse, sigset - signal management
  [XSI]
  #include <signal.h>#include <signal.h>
  int sighold(int sig);
  int sigignore(int sig);
  int sigpause(int sig);
  int sigrelse(int sig);
  void (*sigset(int sig, void (*disp)(int)))(int);
  Use of any of these functions is unspecified in a multi-threaded process.
  The sighold(), sigignore(), sigpause(), sigrelse(), and sigset() functions provide simplified signal management.
  The sigset() function shall shall add sig to the to its original state before returning.].
  Upon successful completion, sigset() shall return SIG_HOLD if the signal had been blocked and the signal's previous disposition if it had not been blocked. Otherwise, SIG_ERR shall be returned and errno set to indicate the error.
  The sigpause() function shall suspend execution of the thread until a signal is received, whereupon it shall return -1 and set errno to [EINTR].
  For all other functions, upon successful completion, 0 shall be returned. Otherwise, -1 shall be returned and errno set to indicate the error.
  These functions shall fail if:
  - >
  First released in Issue 4, Version 2.
  Moved from X/OPEN UNIX extension to BASE.
  The DESCRIPTION is updated to indicate that the sigpause() function restores the process' signal mask to its original state before returning.
  The RETURN VALUE section is updated to indicate that the sigpause() function suspends execution of the process until a signal is received, whereupon it returns -1 and sets errno to [EINTR].
  The DESCRIPTION is updated to avoid use of the term "must" for application requirements.
  References to the wait3() function are removed.
  The XSI functions are split out into their own reference page.