getsid(2) System Calls Manual getsid(2)

getsid - get session ID

Standard C library (libc, -lc)

#include <unistd.h>
pid_t getsid(pid_t pid);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

getsid():

    _XOPEN_SOURCE >= 500
        || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L

getsid() returns the session ID of the process with process ID pid. If pid is 0, getsid() returns the session ID of the calling process.

On success, a session ID is returned. On error, (pid_t) -1 is returned, and errno is set to indicate the error.

A process with process ID pid exists, but it is not in the same session as the calling process, and the implementation considers this an error.
No process with process ID pid was found.

Linux does not return EPERM.

POSIX.1-2008.

POSIX.1-2001, SVr4. Linux 2.0.

See credentials(7) for a description of sessions and session IDs.

getpgid(2), setsid(2), credentials(7)

2024-05-02 Linux man-pages 6.9