работать в фоновом режиме (run in the background)
Имя (Name)
daemon - run in the background
Синопсис (Synopsis)
#include <unistd.h>
int daemon(int nochdir, int noclose);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
daemon():
Since glibc 2.21:
_DEFAULT_SOURCE
In glibc 2.19 and 2.20:
_DEFAULT_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE < 500)
Up to and including glibc 2.19:
_BSD_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE < 500)
Описание (Description)
The daemon() function is for programs wishing to detach
themselves from the controlling terminal and run in the
background as system daemons.
If nochdir is zero, daemon() changes the process's current
working directory to the root directory ("/"); otherwise, the
current working directory is left unchanged.
If noclose is zero, daemon() redirects standard input, standard
output, and standard error to /dev/null; otherwise, no changes
are made to these file descriptors.
Возвращаемое значение (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 daemon() returns zero. If an error occurs,
daemon() returns -1 and sets errno to any of the errors specified
for the fork(2) and setsid(2).
Атрибуты (Attributes)
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│daemon() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
Стандарты (Conforming to)
Not in POSIX.1. A similar function appears on the BSDs. The
daemon() function first appeared in 4.4BSD.
Примечание (Note)
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.
Ошибки (баги) (Bugs)
The GNU C library implementation of this function was taken from
BSD, and does not employ the double-fork technique (i.e.,
fork(2), setsid(2), fork(2)) that is necessary to ensure that the
resulting daemon process is not a session leader. Instead, the
resulting daemon is a session leader. On systems that follow
System V semantics (e.g., Linux), this means that if the daemon
opens a terminal that is not already a controlling terminal for
another session, then that terminal will inadvertently become the
controlling terminal for the daemon.
Смотри также (See also)
fork(2), setsid(2), daemon(7), logrotate(8)
