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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 descripter 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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