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/* Base code taken from http://www-h.eng.cam.ac.uk/help/tpl/unix/fork.html
* Fix for redhat suggested by Ptere Pramberger, peter@pramberger.at */
#include <unistd.h>
#include <sys/wait.h>
#include <stdio.h>
#include <sys/types.h>
#include <signal.h>
void popen_sigchld_handler(int);
int childtermd;
int main() {
char str[1024];
int pipefd[2];
pid_t pid;
int status, died;
if (signal(SIGCHLD, popen_sigchld_handler) == SIG_ERR) {
printf("Cannot catch SIGCHLD\n");
_exit(-1);
}
pipe(pipefd);
switch (pid = fork()) {
case -1:
printf("can't fork\n");
_exit(-1);
case 0: /* this is the code the child runs */
close(1); /* close stdout */
/* pipefd[1] is for writing to the pipe. We want the output
* that used to go to the standard output (file descriptor 1)
* to be written to the pipe. The following command does this,
* creating a new file descriptor 1 (the lowest available)
* that writes where pipefd[1] goes. */
dup(pipefd[1]); /* points pipefd at file descriptor */
/* the child isn't going to read from the pipe, so
* pipefd[0] can be closed */
close(pipefd[0]);
/* These are the commands to run, with success commented. dig and nslookup only problems */
/*execl ("/bin/date","date",0);*/ /* 100% */
/*execl ("/bin/cat", "cat", "/etc/hosts", 0);*/ /* 100% */
/*execl ("/usr/bin/dig", "dig", "redhat.com", 0);*/ /* 69% */
/*execl("/bin/sleep", "sleep", "1", 0);*/ /* 100% */
execl("/usr/bin/nslookup", "nslookup", "redhat.com",
0); /* 90% (after 100 tests), 40% (after 10 tests) */
/*execl ("/bin/ping","ping","-c","1","localhost",0);*/ /* 100% */
/*execl ("/bin/ping","ping","-c","1","192.168.10.32",0);*/ /* 100% */
_exit(0);
default: /* this is the code the parent runs */
close(0); /* close stdin */
/* Set file descriptor 0 (stdin) to read from the pipe */
dup(pipefd[0]);
/* the parent isn't going to write to the pipe */
close(pipefd[1]);
/* Now read from the pipe */
fgets(str, 1023, stdin);
/*printf("1st line output is %s\n", str);*/
/*while (!childtermd);*/ /* Uncomment this line to fix */
died = wait(&status);
/*printf("died=%d status=%d\n", died, status);*/
if (died > 0) {
_exit(0);
} else {
_exit(1);
}
}
}
void popen_sigchld_handler(int signo) {
if (signo == SIGCHLD) {
/*printf("Caught sigchld\n");*/
childtermd = 1;
}
}
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