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setsid — create session and set process group ID
Standard C Library (libc, -lc)
The setsid() system call creates a new session. The calling process is
the session leader of the new session, is the process group leader of a
new process group and has no controlling terminal. The calling process
is the only process in either the session or the process group.
Upon successful completion, the setsid() system call returns the value of
the process group ID of the new process group, which is the same as the
process ID of the calling process. If an error occurs, setsid() returns
-1 and the global variable errno is set to indicate the error.
The setsid() system call will fail if:
[EPERM] The calling process is already a process group leader,
or the process group ID of a process other than the
calling process matches the process ID of the calling
setpgid(2), tcgetpgrp(3), tcsetpgrp(3)
The setsid() system call is expected to be compliant with the ISO/IEC
9945-1:1990 (“POSIX.1”) specification.