Daemon程序

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linux下编写daemon程序有系统库支持,为何有那么多人自己编呢

DAEMON(3)                                                       Linux Programmer’s Manual                                                      DAEMON(3)

NAME
       daemon - run in the background

SYNOPSIS
       #include <unistd.h>

       int daemon(int nochdir, int noclose);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       daemon(): _BSD_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE < 500)

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

       Unless the argument nochdir is non-zero, daemon() changes the current working directory to the root ("/").

       Unless the argument noclose is non-zero, daemon() will redirect standard input, standard output and standard error to /dev/null.

RETURN VALUE
       (This  function  forks,  and  if the fork(2) succeeds, the parent calls _exit(2), so that further errors are seen by the child only.)  On success
       zero will be returned.  If an error occurs, daemon() returns -1 and sets the global variable errno to any of the errors specified for the fork(2)
       and setsid(2).

CONFORMING TO
       Not in POSIX.1-2001.  A similar function appears on the BSDs.  The daemon() function first appeared in 4.4BSD.

NOTES
       The  glibc  implementation  can also return -1 when /dev/null exists but is not a character device with the expected major and minor numbers.  In
       this case errno need not be set.

SEE ALSO
       fork(2), setsid(2)

COLOPHON
       This page is part of release 3.01 of the Linux man-pages project.  A description of the project, and information about  reporting  bugs,  can  be
       found at http://www.kernel.org/doc/man-pages/.

GNU                                                                    2007-07-26                                                              DAEMON(3)
 Manual page daemon(3) line 1/45 (END)


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