SIG_DFL, SIG_IGN

 

C

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Program support utilities

Program termination
abort exit quick_exit (C++11) _Exit (C++11)	atexit at_quick_exit (C++11) EXIT_SUCCESSEXIT_FAILURE
Communicating with the environment
system	getenv
Signals
signal raise sig_atomic_t	SIG_DFLSIG_IGN SIG_ERR
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SIGABRTSIGFPESIGILLSIGINTSIGSEGVSIGTERM
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setjmp
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jmp_buf

 

Defined in header <signal.h>
#define SIG_DFL /*implementation defined*/
#define SIG_IGN /*implementation defined*/

The SIG_DFL and SIG_IGN macros expand into integral expressions that are not equal to an address of any function. The macros define signal handling strategies for signal() function.

Constant	Explanation
SIG_DFL	default signal handling
SIF_IGN	signal is ignored

Example

Run this code

#include <signal.h>
#include <stdio.h>
 
int main(void)
{
    /* using the default signal handler */
    raise(SIGTERM);
    printf("Exit main()\n");   /* never reached */
}

Output:

(none)

Example

Run this code

#include <signal.h>
#include <stdio.h>
 
int main(void)
{
    /* ignoring the signal */
    signal(SIGTERM, SIG_IGN);
    raise(SIGTERM);
    printf("Exit main()\n");
}

Output:

Exit main()

See also

C++ documentation for SIG_DFL, SIG_IGN