sigtstp handler

/**************************************************************** * Filename : sigtstp.c * Author : Saurabh Gupta * Source : http://saurabhgupta0527.blogspot.com/2011/08/posix-signal-tutorial.html * Desc : How to handle SIGTSTP * SIGTSTP in unix * handling SIGTSTP * sigtstp example * Created : PM 09:41 29 October 2011 * Note : ****************************************************************/ #include <signal.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <errno.h> /* for definition of errno */ #include <stdarg.h> /* ISO C variable aruments */ #include <string.h> #define BUFFSIZE 1024 #define MAXLINE 4096 /* max line length */ static void sig_tstp(int); void err_sys(const char *, ...); static void err_doit(int, int, const char *, va_list); int main(void) { int n; char buf[BUFFSIZE]; /* * Only catch SIGTSTP if we're running with a job-control shell. */ if (signal(SIGTSTP, SIG_IGN) == SIG_DFL) { signal(SIGTSTP, sig_tstp); } while ((n = read(STDIN_FILENO, buf, BUFFSIZE)) > 0) if (write(STDOUT_FILENO, buf, n) != n) { err_sys("write error"); } if (n < 0) { err_sys("read error"); } exit(0); } static void sig_tstp(int signo) { /* signal handler for SIGTSTP */ sigset_t mask; /* * Unblock SIGTSTP, since it's blocked while we're handling it. */ sigemptyset(&mask); sigaddset(&mask, SIGTSTP); sigprocmask(SIG_UNBLOCK, &mask, NULL); signal(SIGTSTP, SIG_DFL); /* reset disposition to default */ kill(getpid(), SIGTSTP); /* and send the signal to ourself */ /* * we won't return from the kill until we're continued */ signal(SIGTSTP, sig_tstp); /* reestablish signal handler */ } /* * Fatal error related to a system call. * Print a message and terminate. */ void err_sys(const char *fmt, ...) { va_list ap; va_start(ap, fmt); err_doit(1, errno, fmt, ap); va_end(ap); exit(1); } /* * Print a message and return to caller. * Caller specifies "errnoflag". */ static void err_doit(int errnoflag, int error, const char *fmt, va_list ap) { char buf[MAXLINE]; vsnprintf(buf, MAXLINE, fmt, ap); if (errnoflag) { snprintf(buf+strlen(buf), MAXLINE-strlen(buf), ": %s", strerror(error)); } strcat(buf, "\n"); fflush(stdout); /* in case stdout and stderr are the same */ fputs(buf, stderr); fflush(NULL); /* flushes all stdio output streams */ }
See Also 
POSIX Signal Tutorial and example codes