setsid(S)                      6 January 1993                      setsid(S)


 Name

    setsid - create session and set process ID

 Syntax


    cc  . . .  -lc


    #include  <sys/types.h>
    pid_t setsid ()


 Description

    If the calling process is not already a process group leader, the setsid
    routine creates a new session.  After the routine is called, the calling
    process is the session leader of this new session, the process group
    leader of a new process group, and has no controlling terminal.  The pro-
    cess group ID of the calling process is set to the process ID of the cal-
    ling process.  The calling process is the only process in the new process
    group and in the new session.

 Return value

    Upon successful completion, the setsid routine returns the value of the
    process group ID of the calling process.  If the routine fails, setsid
    returns a value of -1 and errno is set to indicate the appropriate error.

 Diagnostics

    If the following condition occurs, the setsid routine fails and errno is
    set to the corresponding value:

    [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 process.


 See also

    exec(S), exit(S), fork(S), getpid(S), kill(S), setpgid(S), sigaction(S)

 Standards conformance

    setsid conforms with:
    IEEE POSIX Std 1003.1-1990 System Application Program Interface (API) [C
    Language] (ISO/IEC 9945-1);
    and NIST FIPS 151-1.