Working with the Unix OS

Processes II
}
while (!alarmflag)
pause(); /* wait for signal */
printf("loop ends due to alarm signal\n");
void alarmhandler()
{
printf("alarm clock signal was received\n");
alarmflag = 1;
}
/* critical.c - protecting critical code */
#include
#include
main()
{
int (*oldHandler)();
}
oldHandler = signal (SIGINT, SIG_IGN);
printf ("protected from ^C now\n");
sleep(3);
signal (SIGINT, oldHandler); /* restore old handler */
/* limit.c - death of children */
#include
#include
int delay;
void childhandler();
main(int argc, char *argv[])
{
int pid;
signal(SIGCHLD, childhandler);/* signal handler */
pid = fork(); /* duplicate process */
if (pid == 0){ /* child */
execvp(argv[2],&argv[2]); /* execute command */
fprintf(stderr, "limit - should never execute\n");
}
else{ /* parent */
sscanf(argv[1], "%d", &delay);
sleep (delay);
printf ("child %d exceeded limit and is killed\n", pid);
kill(pid, SIGINT); /* kill child */
}
}
limit 5 ls -1
limit 4 sleep 40
/* pulse.c - suspending and resuming processes */
#include
#include
main()
{
int pid1, pid2;
if((pid1=fork())== 0){ /* first child */
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