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