290 lines
6.3 KiB
Groff
290 lines
6.3 KiB
Groff
.\" Copyright (c) 2005 Pawel Jakub Dawidek <pjd@FreeBSD.org>
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd October 16, 2011
|
|
.Dt PIDFILE 3
|
|
.Os
|
|
.Sh NAME
|
|
.Nm pidfile_open ,
|
|
.Nm pidfile_write ,
|
|
.Nm pidfile_close ,
|
|
.Nm pidfile_remove
|
|
.Nd "library for PID files handling"
|
|
.Sh LIBRARY
|
|
.Lb libutil
|
|
.Sh SYNOPSIS
|
|
.In libutil.h
|
|
.Ft "struct pidfh *"
|
|
.Fn pidfile_open "const char *path" "mode_t mode" "pid_t *pidptr"
|
|
.Ft int
|
|
.Fn pidfile_write "struct pidfh *pfh"
|
|
.Ft int
|
|
.Fn pidfile_close "struct pidfh *pfh"
|
|
.Ft int
|
|
.Fn pidfile_remove "struct pidfh *pfh"
|
|
.Ft int
|
|
.Fn pidfile_fileno "struct pidfh *pfh"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm pidfile
|
|
family of functions allows daemons to handle PID files.
|
|
It uses
|
|
.Xr flopen 3
|
|
to lock a pidfile and detect already running daemons.
|
|
.Pp
|
|
The
|
|
.Fn pidfile_open
|
|
function opens (or creates) a file specified by the
|
|
.Fa path
|
|
argument and locks it.
|
|
If
|
|
.Fa pidptr
|
|
argument is not
|
|
.Dv NULL
|
|
and file can not be locked, the function will use it to store a PID of an
|
|
already running daemon or
|
|
.Li -1
|
|
in case daemon did not write its PID yet.
|
|
The function does not write process' PID into the file here, so it can be
|
|
used before
|
|
.Fn fork Ns ing
|
|
and exit with a proper error message when needed.
|
|
If the
|
|
.Fa path
|
|
argument is
|
|
.Dv NULL ,
|
|
.Pa /var/run/ Ns Ao Va progname Ac Ns Pa .pid
|
|
file will be used.
|
|
The
|
|
.Fn pidfile_open
|
|
function sets the O_CLOEXEC close-on-exec flag when opening the pidfile.
|
|
.Pp
|
|
The
|
|
.Fn pidfile_write
|
|
function writes process' PID into a previously opened file.
|
|
.Pp
|
|
The
|
|
.Fn pidfile_close
|
|
function closes a pidfile.
|
|
It should be used after daemon
|
|
.Fn fork Ns s
|
|
to start a child process.
|
|
.Pp
|
|
The
|
|
.Fn pidfile_remove
|
|
function closes and removes a pidfile.
|
|
.Pp
|
|
The
|
|
.Fn pidfile_fileno
|
|
function returns the file descriptor for the open pidfile.
|
|
.Sh RETURN VALUES
|
|
The
|
|
.Fn pidfile_open
|
|
function returns a valid pointer to a
|
|
.Vt pidfh
|
|
structure on success, or
|
|
.Dv NULL
|
|
if an error occurs.
|
|
If an error occurs,
|
|
.Va errno
|
|
will be set.
|
|
.Pp
|
|
.Rv -std pidfile_write pidfile_close pidfile_remove
|
|
.Pp
|
|
The
|
|
.Fn pidfile_fileno
|
|
function returns the low-level file descriptor.
|
|
It returns
|
|
.Li -1
|
|
and sets
|
|
.Va errno
|
|
if a NULL
|
|
.Vt pidfh
|
|
is specified, or if the pidfile is no longer open.
|
|
.Sh EXAMPLES
|
|
The following example shows in which order these functions should be used.
|
|
Note that it is safe to pass
|
|
.Dv NULL
|
|
to
|
|
.Fn pidfile_write ,
|
|
.Fn pidfile_remove ,
|
|
.Fn pidfile_close
|
|
and
|
|
.Fn pidfile_fileno
|
|
functions.
|
|
.Bd -literal
|
|
struct pidfh *pfh;
|
|
pid_t otherpid, childpid;
|
|
|
|
pfh = pidfile_open("/var/run/daemon.pid", 0600, &otherpid);
|
|
if (pfh == NULL) {
|
|
if (errno == EEXIST) {
|
|
errx(EXIT_FAILURE, "Daemon already running, pid: %jd.",
|
|
(intmax_t)otherpid);
|
|
}
|
|
/* If we cannot create pidfile from other reasons, only warn. */
|
|
warn("Cannot open or create pidfile");
|
|
}
|
|
|
|
if (daemon(0, 0) == -1) {
|
|
warn("Cannot daemonize");
|
|
pidfile_remove(pfh);
|
|
exit(EXIT_FAILURE);
|
|
}
|
|
|
|
pidfile_write(pfh);
|
|
|
|
for (;;) {
|
|
/* Do work. */
|
|
childpid = fork();
|
|
switch (childpid) {
|
|
case -1:
|
|
syslog(LOG_ERR, "Cannot fork(): %s.", strerror(errno));
|
|
break;
|
|
case 0:
|
|
pidfile_close(pfh);
|
|
/* Do child work. */
|
|
break;
|
|
default:
|
|
syslog(LOG_INFO, "Child %jd started.", (intmax_t)childpid);
|
|
break;
|
|
}
|
|
}
|
|
|
|
pidfile_remove(pfh);
|
|
exit(EXIT_SUCCESS);
|
|
.Ed
|
|
.Sh ERRORS
|
|
The
|
|
.Fn pidfile_open
|
|
function will fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EEXIST
|
|
Some process already holds the lock on the given pidfile, meaning that a
|
|
daemon is already running.
|
|
If
|
|
.Fa pidptr
|
|
argument is not
|
|
.Dv NULL
|
|
the function will use it to store a PID of an already running daemon or
|
|
.Li -1
|
|
in case daemon did not write its PID yet.
|
|
.It Bq Er ENAMETOOLONG
|
|
Specified pidfile's name is too long.
|
|
.It Bq Er EINVAL
|
|
Some process already holds the lock on the given pidfile, but PID read
|
|
from there is invalid.
|
|
.El
|
|
.Pp
|
|
The
|
|
.Fn pidfile_open
|
|
function may also fail and set
|
|
.Va errno
|
|
for any errors specified for the
|
|
.Xr fstat 2 ,
|
|
.Xr open 2 ,
|
|
and
|
|
.Xr read 2
|
|
calls.
|
|
.Pp
|
|
The
|
|
.Fn pidfile_write
|
|
function will fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EDOOFUS
|
|
Improper function use.
|
|
Probably called before
|
|
.Fn pidfile_open .
|
|
.El
|
|
.Pp
|
|
The
|
|
.Fn pidfile_write
|
|
function may also fail and set
|
|
.Va errno
|
|
for any errors specified for the
|
|
.Xr fstat 2 ,
|
|
.Xr ftruncate 2 ,
|
|
and
|
|
.Xr write 2
|
|
calls.
|
|
.Pp
|
|
The
|
|
.Fn pidfile_close
|
|
function may fail and set
|
|
.Va errno
|
|
for any errors specified for the
|
|
.Xr close 2
|
|
and
|
|
.Xr fstat 2
|
|
calls.
|
|
.Pp
|
|
The
|
|
.Fn pidfile_remove
|
|
function will fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EDOOFUS
|
|
Improper function use.
|
|
Probably called not from the process which made
|
|
.Fn pidfile_write .
|
|
.El
|
|
.Pp
|
|
The
|
|
.Fn pidfile_remove
|
|
function may also fail and set
|
|
.Va errno
|
|
for any errors specified for the
|
|
.Xr close 2 ,
|
|
.Xr fstat 2 ,
|
|
.Xr write 2 ,
|
|
and
|
|
.Xr unlink 2
|
|
system calls and the
|
|
.Xr flopen 3
|
|
library function.
|
|
.Pp
|
|
The
|
|
.Fn pidfile_fileno
|
|
function will fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EDOOFUS
|
|
Improper function use.
|
|
Probably called not from the process which used
|
|
.Fn pidfile_open .
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr open 2 ,
|
|
.Xr daemon 3 ,
|
|
.Xr flopen 3
|
|
.Sh AUTHORS
|
|
.An -nosplit
|
|
The
|
|
.Nm pidfile
|
|
functionality is based on ideas from
|
|
.An John-Mark Gurney Aq jmg@FreeBSD.org .
|
|
.Pp
|
|
The code and manual page was written by
|
|
.An Pawel Jakub Dawidek Aq pjd@FreeBSD.org .
|