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#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
/* https://www.youtube.com/watch?v=gaXigSu72A4 */
static inline void die(const char* msg) {
perror(msg);
exit(EXIT_FAILURE);
}
int main(int argc, char **argv) {
int pdes[2];
pid_t child;
if (pipe(pdes) < 0)
die("pipe()");
if ((child = fork()) < 0)
die("fork()");
if (child == 0) {
/* child process */
close(pdes[0]);
close(1); /* close stdout */
if (dup(pdes[1]) < 0)
die("dup()");
/* now stdout and pdes[1] are equivalent (dup returns lowest free descriptor) */
if (execlp("cat", "cat", "/etc/passwd", NULL) < 0)
die("execlp()");
exit(EXIT_SUCCESS);
}
else {
/* parent process */
close(0); /* close stdin */
close(pdes[1]);
if (dup(pdes[0]) < 0)
die("dup()");
/* now stdin and pdes[0] are equivalent (dup returns lowest free descriptor) */
if (execlp("wc", "wc", "-l", NULL) < 0)
die("execlp()");
exit(EXIT_SUCCESS);
}
return 0;
}
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