NAME    [Toc]    [Back]

       signal - Modifies signal functions

SYNOPSIS    [Toc]    [Back]

       #include <signal.h>

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

STANDARDS    [Toc]    [Back]

       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    [Toc]    [Back]

       Defines the signal.  All signals are valid with the exception
 of SIGKILL and SIGSTOP.  Specifies the address  of  a
       signal handler.

DESCRIPTION    [Toc]    [Back]

       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    [Toc]    [Back]

       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    [Toc]    [Back]

       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    [Toc]    [Back]

       The  signal()  function sets errno to the specified values
       for the following conditions: 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    [Toc]    [Back]

       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)



                                                        signal(2)