signal an exceptional condition


#include <signal.h>
int raise( int condition );


The raise() function signals the exceptional condition indicated by the condition argument. The possible conditions are defined in the <signal.h> header file, and are documented with the signal() function. The signal() function can be used to specify the action that is to take place when such a condition occurs.


The raise() function returns zero when the condition is successfully raised, and a nonzero value otherwise. There may be no return of control following the function call if the action for that condition is to terminate the program or to transfer control using the longjmp() function.


 * This program waits until a SIGINT signal
 * is received.
#include <stdio.h>
#include <signal.h>

sig_atomic_t signal_count;
sig_atomic_t signal_number;

static void alarm_handler( int signum )
    signal_number = signum;

void main()
    unsigned long i;

    signal_count = 0;
    signal_number = 0;
    signal( SIGINT, alarm_handler );

    printf("Signal will be auto-raised on iteration "
       "10000 or hit CTRL-C.\n");
    printf("Iteration:      ");
    for( i = 0; i < 100000; ++i )
      printf("\b\b\b\b\b%*d", 5, i);

      if( i == 10000 ) raise(SIGINT);

      if( signal_count > 0 ) break;

    if( i == 100000 ) {
      printf("\nNo signal was raised.\n");
    } else if( i == 10000 ) {
      printf("\nSignal %d was raised by the "
          "raise() function.\n", signal_number);
    } else {
      printf("\nUser raised the signal.\n",



Interrupt handler No
Signal handler Yes
Thread Yes

See also: