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Asked by FIsh in C Programming Language
I am working with unnamed and named pipes. I have already figured out the unnamed pipe, but have worked up a named pipe program, but it does not work. Could someone please tell me if I am even close.
I need the code to be able to use a named pipe function to have the output of the "ps -ef" command sent through the pipe to the "grep cm415b"command.
so: nova> ps -ef | grep cm415b
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/******************************************
* Class: CMIS 415
* Assignment: P3
* Author:
*Date created: 02 Nov 2009
*Date last modified:
*Comments: Implement an example of pipe-based communication between two UNIX
commands. The commands will be hardcoded inside the program to avoid parsing the
command line.
********************************************/
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
int main() {
int fd;
if (mkfifo("/tmp/fifo", cm415a) == -1) {
perror("error FIFO");
exit(1);
}
switch(fork()) {
case -1:
perror("creating process");
exit(1);
case 0:
close(1);
fd = open("/tmp/fifo", O_WRONLY);
if (fd == -1) {
perror("Opening FIFO for writing");
exit(1);
}
else if (fd != 1) {
fprintf(stderr, "Write descriptor failed");
exit(1);
}
execl("/usr/bin/grep", "grep", "cm415a", (char*) NULL);
perror("Running grep command");
exit(1);
default:
close(0);
fd = open("tmp/fifo", O_RDONLY);
if (fd == -1) {
perror("Opening FIFO for reading");
exit(1);
}
else if (fd != 0) {
fprintf(stderr, "Write descriptor failed");
exit(1);
}
execl("/bin/ps", "ps", "-ef", (char*) NULL);
perror("Running ps command");
exit(1);
}
}
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20091111-EE-VQP-92 - Hierarchy / EE_QW_3_20080625
