A process is running in the foreground if its process group is the same as its terminal's foreground process group.
To put a process in background, you can create a new process group for your process (with setpgid, for example), and then change the controlling terminal's foreground process group to a different one (like the process group id of the parent process, for example). This program will run in the foreground if you pass no arguments to it, and in the background if you pass any arguments:
But as Corona688 said: that's more on that. I tried to show you only the basic idea and code on this subject. Get your Unix Programming book and read it to understand this subject in deep.
These 2 Users Gave Thanks to pflynn For This Post:
hi there,
i was reading about the exec() function. and if i m not wrong, exec() kills your present process and starts a new process in its place. the process id remains the same.
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Ho do I differentiate system call from library call?
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Muru (2 Replies)
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I have to run two commands one after another from a c program. How can i do this with exec system calls. i tried giving them as argument to execv but it is not working.please help
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Discussion started by: demis87
2 Replies
LEARN ABOUT DEBIAN
tcsetpgrp
TCGETPGRP(3) Linux Programmer's Manual TCGETPGRP(3)NAME
tcgetpgrp, tcsetpgrp - get and set terminal foreground process group
SYNOPSIS
#include <unistd.h>
pid_t tcgetpgrp(int fd);
int tcsetpgrp(int fd, pid_t pgrp);
DESCRIPTION
The function tcgetpgrp() returns the process group ID of the foreground process group on the terminal associated to fd, which must be the
controlling terminal of the calling process.
The function tcsetpgrp() makes the process group with process group ID pgrp the foreground process group on the terminal associated to fd,
which must be the controlling terminal of the calling process, and still be associated with its session. Moreover, pgrp must be a
(nonempty) process group belonging to the same session as the calling process.
If tcsetpgrp() is called by a member of a background process group in its session, and the calling process is not blocking or ignoring
SIGTTOU, a SIGTTOU signal is sent to all members of this background process group.
RETURN VALUE
When fd refers to the controlling terminal of the calling process, the function tcgetpgrp() will return the foreground process group ID of
that terminal if there is one, and some value larger than 1 that is not presently a process group ID otherwise. When fd does not refer to
the controlling terminal of the calling process, -1 is returned, and errno is set appropriately.
When successful, tcsetpgrp() returns 0. Otherwise, it returns -1, and errno is set appropriately.
ERRORS
EBADF fd is not a valid file descriptor.
EINVAL pgrp has an unsupported value.
ENOTTY The calling process does not have a controlling terminal, or it has one but it is not described by fd, or, for tcsetpgrp(), this
controlling terminal is no longer associated with the session of the calling process.
EPERM pgrp has a supported value, but is not the process group ID of a process in the same session as the calling process.
CONFORMING TO
POSIX.1-2001.
NOTES
These functions are implemented via the TIOCGPGRP and TIOCSPGRP ioctls.
History
The ioctls appeared in 4.2BSD. The functions are POSIX inventions.
SEE ALSO setpgid(2), setsid(2), credentials(7)COLOPHON
This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
GNU 2003-01-28 TCGETPGRP(3)