daemon()

Run a process in the background

Synopsis:

#include <stdlib.h>

int daemon( int nochdir, 
            int noclose );

Arguments:

nochdir

If this argument is 0, the current working directory is changed to the root directory (/).

noclose

If this argument is 0, standard input, standard output, and standard error are redirected to /dev/null.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The daemon() function allows programs to detach themselves from the controlling terminal and run in the background as system daemons.

This function calls fork() and setsid().

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The controlling terminal behaves as in Unix System V, Release 4. An open() on a terminal device not already associated with another session causes the device to become the controlling terminal for that process. The High Availability Manager can see death messages only from self-attached entities, processes that terminate abnormally, and tasks that are running in session 1. The daemon() function doesn't put the caller into that session; either make your process into a self-attached entity, or use procmgr_daemon() instead if you want to use your application with the HAM. The HAM automatically switches to monitoring the new process that daemon() creates, if the original process was a self-attached entity. For more information, see the High Availability Framework Developer's Guide.

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Returns:

Zero for success, or -1 if an error occurs (errno is set).

Classification:

Legacy Unix

Caveats:

Currently, daemon() is supported only in single-threaded applications. If you create a thread and then call daemon(), the function returns -1 and sets errno to ENOSYS.

See also:

fork(), procmgr_daemon(), setsid()