01-17-2007
display in a child process a command called in the parent one
Hi , Could you tell me if I am right
1. Using fork(), pipe(), execlp() and dup() (see man 2 dup), write a C program executing the command ps -j in a parent process, displaying the result in a child process.
PHP Code:
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <fcntl.h>
#include <termios.h>
int main()
{
int fd[2];
pid_t childpid;
pipe(fd);
if(( childpid=fork()) == 0) {
//child
dup2(fd[1],STDOUT_FILENO);
close(fd[0]);
close(fd[1]);
}
else{ //parent
dup2(fd[0],STDIN_FILENO);
close(fd[0]);
close(fd[1]);
execl("/bin/ps","ps","-j",NULL);
perror("the exec of sort failed");
}
exit(0);
}
Is dup neccessary?
Can't we make this operation just using the pipe itself at 100%?
Thank you very much.
10 More Discussions You Might Find Interesting
1. Programming
Hi everybody,
I'm trying to understand how a parent and child processes interact.
This function( below) basically measures the fork time from the perspective of the parent only.
what i would like to know is how to measure the time from the perspective of parent and child (ie: inserting... (0 Replies)
Discussion started by: tosa
0 Replies
2. UNIX for Advanced & Expert Users
Hi
I am trying to see if there are some options in ps command or if there is a shell script which basically shows you all the processes spawned by a parent process , then all the processes of its child processes and so on down the hierarchy may be like a tree structure. It might be a generic... (6 Replies)
Discussion started by: clifford
6 Replies
3. Shell Programming and Scripting
Hi All,
I have two ksh script. 1st script calls the 2nd script and the second script calls an 'C' program.
I want 1st script to wait until the 'C' program completes.
I cant able to get the process id for the 'C' program (child process) to make the 1st script to wait for the second... (7 Replies)
Discussion started by: sennidurai
7 Replies
4. Shell Programming and Scripting
Hey all, I need to launch a script from within 2 other scripts that can run independently of the two parent scripts... Im having a hard time doing this, if anyone knows how please let me know.
More detail.
ScriptA (bash), ScriptB (ksh), ScriptC (bash)
ScriptA, launches ScriptB
ScirptB,... (7 Replies)
Discussion started by: trey85stang
7 Replies
5. Programming
Hi guys, I'm having some problem here, I'm studying pipes, and i want to create a shell in C and at this point a don't want to use semaphores, instead I want to use tricks. Straight to the doubt: I've a parent and a child process, and both of them has some code to execute, and the child process... (5 Replies)
Discussion started by: pharaoh
5 Replies
6. Programming
This needs to work on HPUX and Linux.
I do a fork and create a child process. During execution of the child process, it is possible child become lost or get killed. That is the reason why I create the child process. However if the child process doesnt get killed, I do want to know the return... (2 Replies)
Discussion started by: usustarr
2 Replies
7. UNIX for Dummies Questions & Answers
Hi,
I have a script that calls other scripts/commands which may or may not spawn other process.
From my understanding, when I do a ps -ef, the highest numbered process ID is supposed to be the parent ID of all the other related child processes, is this correct?
In most or all... (3 Replies)
Discussion started by: newbie_01
3 Replies
8. Emergency UNIX and Linux Support
Hello, everyone.
Here's a program:
pid_t pid = fork();
if (0 == pid) // child process
{
execvp ...;
}
I send a signal (such as SIGINT) to the parent process, the child process receive the signal as well as the parent process.
However I don't want to child process to receive the... (7 Replies)
Discussion started by: jackliang
7 Replies
9. Shell Programming and Scripting
Hi everyone
i am very new to linux , working on bash shell.
I am trying to solve the given problem
1. Create a process and then create children using fork
2. Check the Status of the application for successful running.
3. Kill all the process(threads) except parent and first child... (2 Replies)
Discussion started by: vizz_k
2 Replies
10. Shell Programming and Scripting
HI i would like to know how i can simulate a shell scripts for my requirement.
example
Server name child Process id Parent Process id
Vpesh 16013 15637
Server name child Process id Parent Process id
Vpesh 16014 15637
Server name child... (1 Reply)
Discussion started by: vpesh
1 Replies