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| author | Michael Kerrisk <mtk.manpages@gmail.com> | 2014-11-25 23:31:55 +0100 |
|---|---|---|
| committer | Michael Kerrisk <mtk.manpages@gmail.com> | 2014-12-05 06:09:31 +0100 |
| commit | d6c9f01b6440e57ba9e737dd13648465087ecc75 (patch) | |
| tree | b0741285ab6270981e0120edbf06604014a12464 | |
| parent | a00ca3d5a071ff4c17090361a7375d1c620865ea (diff) | |
| download | man-pages-d6c9f01b6440e57ba9e737dd13648465087ecc75.tar.gz | |
setsid.2: Rewrite some pieces and add some details
Among other changes, add an explanation of why setsid() can't
be called from a process group leader
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
| -rw-r--r-- | man2/setsid.2 | 25 |
1 files changed, 17 insertions, 8 deletions
diff --git a/man2/setsid.2 b/man2/setsid.2 index 40a8fe98f0..52bc88e02d 100644 --- a/man2/setsid.2 +++ b/man2/setsid.2 @@ -1,5 +1,6 @@ .\" Copyright Michael Haardt (michael@cantor.informatik.rwth-aachen.de) .\" Sat Aug 27 20:43:50 MET DST 1994 +.\" and Copyright (C) 2014, Michael Kerrisk <mtk.manpages@gmail.com> .\" .\" %%%LICENSE_START(GPLv2+_DOC_FULL) .\" This is free documentation; you can redistribute it and/or @@ -41,13 +42,15 @@ setsid \- creates a session and sets the process group ID .BR setsid () creates a new session if the calling process is not a process group leader. -The calling process is the leader of the new -session, the process group leader of the new process group, and has no -controlling terminal. -The process group ID and session ID of the calling -process are set to the PID of the calling process. +The calling process is the leader of the new session +(i.e., its session ID is made the same as it process ID). +The calling process also becomes +the process group leader of a new process group in the session +(i.e., its process group ID is made the same as it process ID). + The calling process will be the only process in -this new process group and in this new session. +the new process group and in the new session. +The new session has no controlling terminal. .SH RETURN VALUE On success, the (new) session ID of the calling process is returned. On error, @@ -71,8 +74,14 @@ inherits its parent's session ID. The session ID is preserved across an .BR execve (2). -A process group leader is a process with process group ID equal -to its PID. +A process group leader is a process whose process group ID equals its PID. +Disallowing a process group leader from calling +.BR setsid() +prevents the possibility that a process group leader places itself +in a new session while other processes in the process group remain +in the original session; +such a scenario would break the strict +two-level hierarchy of sessions and process groups. In order to be sure that .BR setsid () will succeed, |