62 lines
1.7 KiB
C
62 lines
1.7 KiB
C
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#include <stdio.h>
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#include <signal.h>
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#include <unistd.h>
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#include <stdlib.h>
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int signal_received = 0;
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// Handle multiple different signals in a single handler. Note that
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// the signal handler is NOT reset in the function but still
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// works. This is the behavior of most modern implementations.
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void handle_usr_signals(int signo) { // argument is signal number
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signal_received = 1;
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if (signo == SIGUSR1){ // check for signal type 1
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printf("received SIGUSR1\n");
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}
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else if (signo == SIGUSR2){ // check for signal type 2
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printf("received SIGUSR2\n");
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}
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else{ // this should not be reachable
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printf("signo %d: Wait, how did I get here?\n",signo);
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exit(1);
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}
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}
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// Required to check the result of using the signal() function
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typedef void (*sighandler_t)(int);
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// main() function: set up signal handlers then sleep for an
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// interval. Can be woken up by some signals.
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//
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// Note also default disposition for signals like CONT which are
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// ignored while the program is running.
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int main(void) {
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// Set signal handler and check result
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sighandler_t result = signal(SIGUSR1, handle_usr_signals);
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if(result == SIG_ERR){
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perror("couldn't set handler for SIGUSR1");
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exit(1);
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}
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// Short hand for set/check result
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if (signal(SIGUSR2, handle_usr_signals) == SIG_ERR){
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perror("couldn't set handler for SIGUSR2");
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exit(1);
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}
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while(1){
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sleep(4); // Sleep until a woken by a signal or 4 seconds passes
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if(signal_received == 1){
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printf("Signalled! Back to sleep now\n");
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signal_received = 0;
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}
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else{
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printf("Woke up after sleeping. Back to bed\n");
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}
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}
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}
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