tcsetpgrp

Synopsis

#include <unistd.h>

int tcsetpgrp(int fildes, pid_t pgid_id);

Status

Partially implemented

Conformance

IEEE Std 1003.1-2017

Description

tcsetpgrp() - set the foreground process group ID

If the process has a controlling terminal, tcsetpgrp() shall set the foreground process group ID associated with the terminal to pgid_id. The application shall ensure that the file associated with fildes is the controlling terminal of the calling process and the controlling terminal is currently associated with the session of the calling process. The application shall ensure that the value of pgid_id matches a process group ID of a process in the same session as the calling process.

Attempts to use tcsetpgrp() from a process which is a member of a background process group on a fildes associated with its controlling terminal shall cause the process group to be sent a SIGTTOU signal. If the calling thread is blocking SIGTTOU signals or the process is ignoring SIGTTOU signals, the process shall be allowed to perform the operation, and no signal is sent.

Return value

Upon successful completion, 0 shall be returned. Otherwise, -1 shall be returned and errno set to indicate the error.

Errors

The tcsetpgrp() function shall fail if:

  • EBADF - The fildes argument is not a valid file descriptor.

  • EINVAL - This implementation does not support the value in the pgid_id argument.

  • EIO - The process group of the writing process is orphaned, the calling thread is not blocking SIGTTOU, and the process is not ignoring SIGTTOU.

  • EINVAL - The file associated with fildes is not a terminal, and the server handling it reports unsupported requests with EINVAL (see POSIX deviations).

  • ENOTTY - The calling process does not have a controlling terminal, or the file is not the controlling terminal, or the controlling terminal is no longer associated with the session of the calling process.

  • EPERM - The value of pgid_id is a value supported by the implementation, but does not match the process group ID of a process in the same session as the calling process.

POSIX deviations

If the file associated with fildes is not a terminal, the error reported by tcsetpgrp() depends on the server handling the file. The function is implemented on top of ioctl(), and the kernel forwards every request to the server without checking the type of the file. Servers that do not handle terminal requests report them either with ENOTTY (for example files in jffs2) or with EINVAL (for example pipes and files in dummyfs).