Unix pipes: example 2
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/* This sample program
creates the same affect
as typing ps -aux|grep <username>
*/
#include <stdio.h>
char *getlogin();
main() {
FILE *fp;
int pipefds[2];
int pid;
char *username;
if((username = getlogin()) == NULL) {
fprintf(stderr, "myps: user name not set.\n");
exit(1);
}
if(pipe(pipefds) < 0) {
perror("myps");
exit(1);
}
if((pid = fork()) < 0) {
perror("myps");
exit(1);
}
if(pid == 0) {
/* close standard input */
close(0);
/* duplicate our pipe to be standard input */
dup(pipefds[0]);
/* close the pipe */
close(pipefds[0]);
close(pipefds[1]);
execl("/bin/grep", "grep", username, (char *) 0);
perror("myps");
exit(1);
}
/* close the read file descriptor */
close(pipefds[0]);
/* close standard output */
close(1);
/* duplicate the write file descriptor to std out */
dup(pipefds[1]);
/* close the write file descriptor */
close(pipefds[1]);
fp = fdopen(pipefds[1], "w");
execl("/bin/ps", "ps", "-aux", (char *) 0);
perror("myps");
exit(1);
}
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cs153@csif.cs.ucdavis.edu.
Department of Computer Science
University of California at Davis
Davis, CA 95616-8562
Page last modified on 1/23/97