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SIGSET(3) Linux Programmer's Manual SIGSET(3)


     sigset, sighold, sigrelse, sigignore - System V signal API


     #include <signal.h>
     typedef void (*sighandler_t)(int);
     sighandler_t sigset(int sig, sighandler_t disp);
     int sighold(int sig);
     int sigrelse(int sig);
     int sigignore(int sig);
 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
     sigset(), sighold(), sigrelse(), sigignore():
         _XOPEN_SOURCE >= 500


     These  functions are provided in glibc as a compatibility interface for
     programs that make use of the historical System V signal API.  This API
     is  obsolete:  new applications should use the POSIX signal API (sigac-
     tion(2), sigprocmask(2), etc.)
     The sigset() function modifies the disposition of the signal sig.   The
     disp  argument  can be the address of a signal handler function, or one
     of the following constants:
            Reset the disposition of sig to the default.
            Ignore sig.
            Add sig to the process's signal mask, but leave the  disposition
            of sig unchanged.
     If disp specifies the address of a signal handler, then sig is added to
     the process's signal mask during execution of the handler.
     If disp was specified as a value  other  than  SIG_HOLD,  then  sig  is
     removed from the process's signal mask.
     The dispositions for SIGKILL and SIGSTOP cannot be changed.
     The sighold() function adds sig to the calling process's signal mask.
     The  sigrelse()  function removes sig from the calling process's signal
     The sigignore() function sets the disposition of sig to SIG_IGN.


     On success, sigset() returns SIG_HOLD if sig  was  blocked  before  the
     call, or the signal's previous disposition if it was not blocked before
     the call.  On error, sigset() returns -1, with errno  set  to  indicate
     the error.  (But see BUGS below.)
     The  sighold(),  sigrelse(), and sigignore() functions return 0 on suc-
     cess; on error, these functions return -1 and set errno to indicate the


     For sigset() see the ERRORS under sigaction(2) and sigprocmask(2).
     For sighold() and sigrelse() see the ERRORS under sigprocmask(2).
     For sigignore(), see the errors under sigaction(2).


     For   an   explanation   of   the  terms  used  in  this  section,  see
     |Interface               | Attribute     | Value   |
     |sigset(), sighold(),    | Thread safety | MT-Safe |
     |sigrelse(), sigignore() |               |         |


     SVr4, POSIX.1-2001, POSIX.1-2008.  These functions are obsolete: do not
     use them in new programs.  POSIX.1-2008 marks  sighold(),  sigignore(),
     sigpause(3), sigrelse(), and sigset() as obsolete, recommending the use
     of sigaction(2), sigprocmask(2), pthread_sigmask(3), and  sigsuspend(2)


     These functions appeared in glibc version 2.1.
     The  sighandler_t type is a GNU extension; it is used on this page only
     to make the sigset() prototype more easily readable.
     The sigset() function provides reliable signal handling  semantics  (as
     when calling sigaction(2) with sa_mask equal to 0).
     On  System  V,  the signal() function provides unreliable semantics (as
     when calling sigaction(2) with sa_mask equal to SA_RESETHAND | SA_NODE-
     FER).   On  BSD,  signal()  provides  reliable semantics.  POSIX.1-2001
     leaves these aspects of signal() unspecified.  See signal(2)  for  fur-
     ther details.
     In  order  to wait for a signal, BSD and System V both provided a func-
     tion named sigpause(3), but this function has a different  argument  on
     the two systems.  See sigpause(3) for details.


     In  versions  of glibc before 2.2, sigset() did not unblock sig if disp
     was specified as a value other than SIG_HOLD.
     In versions of glibc before 2.5, sigset() does not correctly return the
     previous  disposition  of  the  signal in two cases.  First, if disp is
     specified as  SIG_HOLD,  then  a  successful  sigset()  always  returns
     SIG_HOLD.   Instead,  it  should return the previous disposition of the
     signal (unless the signal was blocked, in which case SIG_HOLD should be
     returned).  Second, if the signal is currently blocked, then the return
     value of a successful sigset() should be SIG_HOLD.  Instead, the previ-
     ous  disposition  of  the signal is returned.  These problems have been
     fixed since glibc 2.5.


     kill(2), pause(2), sigaction(2), signal(2),  sigprocmask(2),  raise(3),
     sigpause(3), sigvec(3), signal(7)


     This  page  is  part of release 4.16 of the Linux man-pages project.  A
     description of the project, information about reporting bugs,  and  the
     latest     version     of     this    page,    can    be    found    at

Linux 2017-09-15 SIGSET(3)

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