setsid(2)setsid(2)NAMEsetsid - set session ID
SYNOPSIS
#include <sys/types.h>
#include <unistd.h>
pid_t setsid(void);
DESCRIPTION
If the calling process is not already a process group leader, setsid sets
the process group ID and session ID of the calling process to the process
ID of the calling process, and releases the process's controlling
terminal.
setsid will fail and return an error if the following is true:
EPERM The calling process is already a process group leader, or
there are processes other than the calling process whose
process group ID is equal to the process ID of the calling
process.
SEE ALSOintro(2), exec(2), exit(2), fork(2), getpid(2), getpgid(2), getsid(2),
setpgid(2), setpgrp, signal(2), sigsend(2), sigaction(2).
NOTES
If the calling process is the last member of a pipeline started by a job
control shell, the shell may make the calling process a process group
leader. The other processes of the pipeline become members of that
process group. In this case, the call to setsid will fail. For this
reason, a process that calls setsid and expects to be part of a pipeline
should always first fork; the parent should exit and the child should
call setsid, thereby insuring that the process will work reliably when
started by both job control shells and non-job control shells.
DIAGNOSTICS
Upon successful completion, setsid returns the calling process's session
ID. Otherwise, a value of -1 is returned and errno is set to indicate
the error.
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