sigismember()--Test for Signal in Signal Set

 #include <signal.h>

 int sigismember( const sigset_t *set, int signo );   

The sigismember() function is part of a family of functions that manipulate signal sets. Signal sets are data objects that let a thread keep track of groups of signals. For example, a thread might create a signal set to record which signals it is blocking, and another signal set to record which signals are pending. Signal sets are used to manipulate groups of signals used by other functions (such as sigprocmask()) or to examine signal sets returned by other functions (such as sigpending()).

sigismember() tests whether a signal number specified by signo is a member of a signal set specified by set.

Authorities and Locks

None.

Parameters

*set

(Input) A pointer to a signal set.

signo

(Input) A signal from the list defined in Control Signals Table.

Return Value

Error Conditions

If sigismember() is not successful, errno usually indicates the following error. Under some conditions, errno could indicate an error other than that listed here.

[EINVAL]

The value specified for the argument is not correct.

A function was passed incorrect argument values, or an operation was attempted on an object and the operation specified is not supported for that type of object.

An argument value is not valid, out of range, or NULL.

The value of signo is not within the range of valid signals or specifies a signal that is not supported.

Related Information

• The <signal.h> file (see Header Files for UNIX-Type Functions)
  
  
• sigaction()--Examine and Change Signal Action
  
  
• sigaddset()--Add Signal to Signal Set
  
  
• sigdelset()--Delete Signal from Signal Set
  
  
• sigemptyset()--Initialize and Empty Signal Set
  
  
• sigfillset()--Initialize and Fill Signal Set
  
  
• sigprocmask()--Examine and Change Blocked Signals
  
  
• sigpending()--Examine Pending Signals
  
  
• sigsuspend()--Wait for Signal
  
  
• sigtimedwait()--Synchronously Accept a Signal for Interval of Time
  
  
• sigwait()--Synchronously Accept a Signal
  
  
• sigwaitinfo()--Synchronously Accept a Signal and Signal Data

Example

See Code disclaimer information for information pertaining to code examples.

The following example uses the sigismember() function to test for the presence of signals in a signal set:

#include <stdio.h>
#include <signal.h>

void check( sigset_t set, int signo, char *signame ) {

    printf( "%s is ", signame );
    if( !sigismember( &set, signo ) )
      printf( "not ");
    printf( "in the set" );
}

int main( int argc, char *argv[] ) {

    sigset_t sigset;

    sigemptyset( &sigset );

    sigaddset( &sigset, SIGUSR1 );
    sigaddset( &sigset, SIGKILL );
    sigaddset( &sigset, SIGCHLD );

    check( sigset, SIGUSR1, "SIGUSR1" );
    check( sigset, SIGUSR2, "SIGUSR2" );
    check( sigset, SIGCHLD, "SIGCHLD" );
    check( sigset, SIGFPE,  "SIGFPE" );
    check( sigset, SIGKILL, "SIGKILL" );

    return( 0 );
}

Output:

    SIGUSR1 is in the set
    SIGUSR2 is not in the set
    SIGCHLD is in the set
    SIGFPE is not in the set
    SIGKILL is in the set