setpgid()
QNX SDP8.0C Library ReferenceAPIDeveloper
Join or create a process group
Synopsis:
#include <unistd.h>
int setpgid( pid_t pid,
pid_t pgid );
This function is declared in <process.h>, which <unistd.h> includes.
Arguments:
- pid
- 0, or the ID of the process whose process group you want to set.
- pgid
- 0, or the process group ID that you want to join or create.
Library:
libc
Use the -l c option to qcc to link against this library. This library is usually included automatically.
Description:
The setpgid() function is used either to join an existing process group or to create a new process group within the session of the calling process. The process group ID of a session leader doesn't change.
The following definitions are worth mentioning:
- Process
- An executing instance of a program, identified by a nonnegative integer called a process ID.
- Process group
- A collection of one or more processes, with a unique process group ID. A process group ID is a positive integer.
On successful completion, the process group ID of the process with a process ID matching pid is set to pgid. As a special case, you can specify either pid or pgid as zero, meaning that the process ID of the calling process is to be used.
Returns:
- 0
- Success.
- -1
- An error occurred; errno is set.
Errors:
- EACCES
- The value of the pid argument matches the process ID of a child process of the calling process, and the child process has successfully executed one of the exec*() functions.
- EINVAL
- The value of pgid is less than zero.
- ENOSYS
- The setpgid() function isn't supported by this implementation (included for POSIX compatibility).
- EPERM
- The calling process doesn't have sufficient privilege to set the process group id pgid on process pid.
- ESRCH
- The process pid doesn't exist.
Examples:
/*
* Join the process group of the calling process.
*/
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
int main( void )
{
if( setpgid( getpid(), 0 ) == -1 ) {
perror( "setpgid" );
}
printf( "%d belongs to process group %d\n",
getpid(), getpgrp() );
return EXIT_SUCCESS;
}
Classification:
| Safety: | |
|---|---|
| Cancellation point | No |
| Signal handler | Yes |
| Thread | Yes |
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