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signal(2)
NAME
  signal - Modifies signal functions

SYNOPSIS
  #include <signal.h>

  void (*signal(
	  int sig,
	  void (*function)(int)) (int) );

STANDARDS
  Interfaces documented on this reference page conform to industry standards
  as follows:

  signal():  XPG4, XPG4-UNIX

  Refer to the standards(5) reference page for more information about
  industry standards and associated tags.

PARAMETERS
  sig Defines the signal.  All signals are valid with the exception of
      SIGKILL and SIGSTOP.

  function
      Specifies the address of a signal handler.

DESCRIPTION
  The signal function provides compatibility for older versions of the
  operating system whose function is a subset of the sigaction function. The
  signal function sets the action associated with a signal. The function
  parameter uses the values SIG_DFL, SIG_IGN, or it can point to an address
  of a signal handler.

  A SIG_DFL value specifies the default action that is to be taken when the
  signal is delivered.	A value of SIG_IGN specifies that the signal has no
  effect on the receiving process. A pointer to a function requests that the
  signal be caught; that is, the signal should cause the function to be
  called. These actions are more fully described in the <signal.h> file.

NOTES
  The sigaction() function provides a more comprehensive and reliable
  mechanism for controlling signals and is recommended instead of signal()
  for new applications.

  [Tru64 UNIX]	The effect of calling the signal function behavior differs
  depending on whether the calling program is linked with either of the
  special libraries, libbsd or libsys5, which supply BSD or System V
  signaling characteristics respectively. If neither library is used, the
  behavior is the same as that of the sigaction function with all the flags
  set to 0 (zero).  If the libsys5 library is used (through compilation with
  the -lsys5 switch), then the specified signal is not blocked from delivery
  when the handler is entered, and the disposition of the signal reverts to
  SIG_DFL when the signal is delivered.	 If the libbsd library or the
  bsd_signal() function is used, the behavior is the same as that of the
  sigaction() function with the SA_RESTART flag set.

  [Tru64 UNIX]	When compiled in the X/Open UNIX environment, calls to the
  signal() function are internally renamed by prepending _E to the function
  name.	 When you are debugging a module that includes the libc version of
  the signal() function and for which _XOPEN_SOURCE_EXTENDED has been
  defined, use _Esignal to refer to the signal() call.	See standards(5) for
  information on when the _XOPEN_SOURCE_EXTENDED macro is defined.

RETURN VALUES
  Upon successful completion of the signal function, the value of the
  previous signal action is returned. Otherwise, SIG_ERR is returned and
  errno is set to indicate the error.

ERRORS
  The signal() function sets errno to the specified values for the following
  conditions:

  [EINVAL]
      The sig parameter is not a valid signal number or an attempt was made
      to catch a signal that cannot be caught or to ignore a signal that
      cannot be ignored.

SEE ALSO
  Commands:  kill(1)

  Functions:  acct(2), bsd_signal(2), exit(2), kill(2), pause(3), ptrace(2),
  setjmp(3), sigaction(2), sigblock(2), sigpause(3), sigprocmask(2),
  sigstack(2), sigsuspend(2), sigvec(2), umask(2), wait(2)

  Files:  signal(4)

  Standards:  standards(5)

Index for Section 2

Alphabetical listing for S

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