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Old 11-02-2012, 10:11 AM   #1
mrneo
LQ Newbie
 
Registered: Nov 2012
Posts: 4

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Question execlp() doesnt wait for the input??


i am just starting with programming in linux.i am trying to fork a child process and replace it with the "sort" program. below is the code iam using for this.

i expeceted that when i invoked sort programm it would wait for me to give it input but instead the program just terminates.

how can i make the child process take input interactively?

#include <stdio.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
int main ()
{
pid_t pid;
pid = fork ();
if (pid == (pid_t) 0) {
execlp ("sort","sort",0);
}
else {
waitpid (pid, NULL, 0);
}
return 0;
}
 
Old 11-02-2012, 10:15 AM   #2
linosaurusroot
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Registered: Oct 2012
Distribution: OpenSuSE,RHEL,Fedora,OpenBSD
Posts: 979
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Rep: Reputation: 235Reputation: 235Reputation: 235
I don't see any code in your post. Why isn't this in the programming forum?

Code:
execl("/bin/sort", "sort" , "input_filename",  (char *)0 );
That won't wait because the input file should be there already.
Code:
execl("/bin/sort", "sort" , "-",  (char *)0 );
That should take standard input.
 
Old 11-02-2012, 11:22 AM   #3
mrneo
LQ Newbie
 
Registered: Nov 2012
Posts: 4

Original Poster
Rep: Reputation: Disabled
@linosaurusroot
i missed to paste the code first time i submitted the code but then immediately i did edit and pasted it. however below is the code. i tried execl("/bin/sort", "sort" , "-", (char *)0 ) but it didnt work, the program just terminates.

#include <stdio.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
int main ()
{
pid_t pid;
pid = fork ();
if (pid == (pid_t) 0) {
execlp ("sort","sort",0);
}
else {
waitpid (pid, NULL, 0);
}
return 0;
}
 
Old 11-03-2012, 06:18 AM   #4
mrneo
LQ Newbie
 
Registered: Nov 2012
Posts: 4

Original Poster
Rep: Reputation: Disabled
sorry about the confusion, my code has a line which was duplicating the standard input of child process to a stream created in the parent process.
 
  


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