Add a family of functions for reliable pidfiles handling.
Idea from: jmg Discussed on: arch@
This commit is contained in:
parent
4986c6d8e2
commit
412fa8f114
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=149423
@ -8,15 +8,16 @@ CFLAGS+=-DLIBC_SCCS -I${.CURDIR} -I${.CURDIR}/../libc/gen/
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CFLAGS+=-DINET6
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SRCS= _secure_path.c auth.c fparseln.c humanize_number.c login.c \
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login_auth.c login_cap.c login_class.c login_crypt.c login_ok.c \
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login_times.c login_tty.c logout.c logwtmp.c property.c pty.c \
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pw_util.c realhostname.c stub.c \
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login_times.c login_tty.c logout.c logwtmp.c \
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pidfile.c property.c pty.c pw_util.c realhostname.c stub.c \
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trimdomain.c uucplock.c
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INCS= libutil.h login_cap.h
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MAN+= login.3 login_auth.3 login_tty.3 logout.3 logwtmp.3 pty.3 \
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login_cap.3 login_class.3 login_times.3 login_ok.3 \
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_secure_path.3 uucplock.3 property.3 auth.3 realhostname.3 \
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realhostname_sa.3 trimdomain.3 fparseln.3 humanize_number.3
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realhostname_sa.3 trimdomain.3 fparseln.3 humanize_number.3 \
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pidfile.3
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MAN+= login.conf.5 auth.conf.5
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MLINKS+= property.3 properties_read.3 property.3 properties_free.3
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MLINKS+= property.3 property_find.3
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@ -39,5 +40,9 @@ MLINKS+=login_ok.3 auth_ttyok.3 login_ok.3 auth_hostok.3 \
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MLINKS+=login_auth.3 auth_checknologin.3 login_auth.3 auth_cat.3
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MLINKS+=uucplock.3 uu_lock.3 uucplock.3 uu_lock_txfr.3 \
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uucplock.3 uu_unlock.3 uucplock.3 uu_lockerr.3
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MLINKS+=pidfile.3 pidfile_open.3 \
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pidfile.3 pidfile_write.3 \
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pidfile.3 pidfile_close.3 \
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pidfile.3 pidfile_remove.3
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.include <bsd.lib.mk>
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@ -49,6 +49,16 @@ typedef struct _property {
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char *value;
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} *properties;
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#ifdef _SYS_PARAM_H_
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/* for pidfile.c */
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struct pidfh {
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int pf_fd;
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char pf_path[MAXPATHLEN + 1];
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__dev_t pf_dev;
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ino_t pf_ino;
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};
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#endif
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/* Avoid pulling in all the include files for no need */
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struct termios;
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struct winsize;
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@ -102,6 +112,13 @@ struct passwd *pw_scan(const char *_line, int _flags);
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const char *pw_tempname(void);
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int pw_tmp(int _mfd);
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#endif
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#ifdef _SYS_PARAM_H_
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struct pidfh *pidfile_open(const char *path, mode_t mode, pid_t *pidptr);
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int pidfile_write(struct pidfh *pfh);
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int pidfile_close(struct pidfh *pfh);
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int pidfile_remove(struct pidfh *pfh);
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#endif
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__END_DECLS
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#define UU_LOCK_INUSE (1)
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227
lib/libutil/pidfile.3
Normal file
227
lib/libutil/pidfile.3
Normal file
@ -0,0 +1,227 @@
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.\" Copyright (c) 2005 Pawel Jakub Dawidek <pjd@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd August 22, 2005
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.Dt PIDFILE 3
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.Os
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.Sh NAME
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.Nm pidfile_open ,
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.Nm pidfile_write ,
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.Nm pidfile_close ,
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.Nm pidfile_remove
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.Nd library for PID files handling
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.Sh LIBRARY
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.Lb libutil
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.Sh SYNOPSIS
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.In sys/param.h
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.In libutil.h
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.Ft struct pidfh *
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.Fn pidfile_open "const char *path" "mode_t mode" "pid_t *pidptr"
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.Ft int
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.Fn pidfile_write "struct pidfh *pfh"
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.Ft int
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.Fn pidfile_close "struct pidfh *pfh"
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.Ft int
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.Fn pidfile_remove "struct pidfh *pfh"
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.Sh DESCRIPTION
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The
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.Nm libpidfile
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library provides functions for daemons to handle file with PID.
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It uses
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.Xr flock 2
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to lock pidfile and detect already running daemons.
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.Pp
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The
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.Fn pidfile_open
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function opens (or creates) a file specified by
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.Fa path
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argument and locks it with
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.Xr flock 2
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syscall.
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If file can not be locked, PID of already running daemon is returned in
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.Fa pidptr
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argument (if it is not NULL).
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The function doesn't write process' PID into the file here, so it can be
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used before fork()ing and exit with proper error message when needed.
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If
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.Fa path
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argument is NULL,
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.Pa /var/run/<progname>.pid
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file will be used.
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.Pp
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The
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.Fn pidfile_write
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function write process' PID into previously opened file.
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.Pp
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The
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.Fn pidfile_close
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function closes pidfile.
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It should be used after daemon fork()s to start a child process.
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.Pp
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The
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.Fn pidfile_remove
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function closes and removes pidfile.
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.Sh RETURN VALUES
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The
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.Fn pidfile_open
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function return a valid pointer to a pidfh structure on success or
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.Dv NULL
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if an error occurs.
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If an error does occur,
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.Va errno
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will be set.
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.Rv -std pidfile_write pidfile_close pidfile_remove
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.Sh EXAMPLES
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The following example shows in which order those functions should be used.
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.Bd -literal
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struct pidfh *pfh;
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pid_t otherpid, childpid;
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pfh = pidfile_open("/var/run/daemon.pid", 0644, &otherpid);
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if (pfh == NULL) {
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if (errno == EEXIST)
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errx(EXIT_FAILURE, "Daemon already running, pid: %d.", otherpid);
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/* If we cannot create pidfile from other reasons, only warn. */
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warn("Cannot open or create pidfile");
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}
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if (daemon(0, 0) == -1) {
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warn("Cannot daemonize");
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pidfile_remove(pfh);
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exit(EXIT_FAILURE);
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}
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pidfile_write(pfh);
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for (;;) {
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/* Do work. */
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childpid = fork();
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switch (childpid) {
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case -1:
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syslog(LOG_ERR, "Cannot fork(): %s.", strerror(errno));
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break;
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case 0:
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pidfile_close(pfh);
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/* Do child work. */
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break;
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default:
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syslog(LOG_INFO, "Child %d started.", childpid);
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break;
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}
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}
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pidfile_remove(pfh);
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exit(EXIT_SUCCESS);
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.Ed
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.Sh ERRORS
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The
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.Fn pidfile_open
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function will fail if:
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.Bl -tag -width Er
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.It Bq Er EEXIST
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Some process already holds the lock on the given pidfile, which means,
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daemon is already running.
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.It Bq Er ENAMETOOLONG
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Specified pidfile's name is too long.
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.It Bq Er EINVAL
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Some process already holds the lock on the given pidfile, but PID read
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from there is invalid.
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.El
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.Pp
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The
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.Fn pidfile_open
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function may also fail and set
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.Va errno
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for any errors specified for the
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.Xr fstat 2 ,
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.Xr open 2 ,
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.Xr read 2
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routines.
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.Pp
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The
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.Fn pidfile_write
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function will fail if:
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.Bl -tag -width Er
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.It Bq Er EDOOFUS
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Inproper function use.
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Probably called before
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.Fn pidfile_open .
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.El
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.Pp
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The
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.Fn pidfile_write
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function may also fail and set
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.Va errno
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for any errors specified for the
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.Xr fstat 2 ,
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.Xr ftruncate 2 ,
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.Xr write 2
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routines.
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.Pp
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The
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.Fn pidfile_close
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function may fail and set
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.Va errno
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for any errors specified for the
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.Xr close 2 ,
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.Xr fstat 2
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routines.
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.Pp
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The
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.Fn pidfile_remove
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function will fail if:
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.Bl -tag -width Er
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.It Bq Er EDOOFUS
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Inproper function use.
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Probably called not from the process which made
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.Fn pidfile_write .
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.El
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.Pp
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The
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.Fn pidfile_remove
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function may also fail and set
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.Va errno
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for any errors specified for the
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.Xr close 2 ,
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.Xr flock 2 ,
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.Xr fstat 2 ,
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.Xr write 2 ,
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.Xr unlink 2
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routines.
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.Pp
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.Sh SEE ALSO
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.Xr flock 2 ,
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.Xr open 2 ,
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.Xr daemon 3
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.Sh AUTHORS
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.An -nosplit
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The
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.Xr pidfile 3
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functionality is based on ideas from
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.An John-Mark Gurney Aq jmg@FreeBSD.org .
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.Pp
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The code and manual page was written by
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.An Pawel Jakub Dawidek Aq pjd@FreeBSD.org .
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246
lib/libutil/pidfile.c
Normal file
246
lib/libutil/pidfile.c
Normal file
@ -0,0 +1,246 @@
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/*-
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* Copyright (c) 2005 Pawel Jakub Dawidek <pjd@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/file.h>
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#include <sys/stat.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <string.h>
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#include <err.h>
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#include <errno.h>
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#include <libutil.h>
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static int _pidfile_remove(struct pidfh *pfh, int freeit);
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static int
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pidfile_verify(struct pidfh *pfh)
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{
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struct stat sb;
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int fd;
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if (pfh == NULL || pfh->pf_fd == -1)
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return (EDOOFUS);
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/*
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* Check remembered descriptor.
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*/
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if (fstat(pfh->pf_fd, &sb) == -1)
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return (errno);
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if (sb.st_dev != pfh->pf_dev || sb.st_ino != pfh->pf_ino)
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return (EDOOFUS);
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return (0);
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}
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static int
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pidfile_read(const char *path, pid_t *pidptr)
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{
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char buf[16], *endptr;
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int error, fd, i;
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fd = open(path, O_RDONLY);
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if (fd == -1)
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return (errno);
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i = read(fd, buf, sizeof(buf) - 1);
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error = errno; /* Remember errno in case close() wants to change it. */
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close(fd);
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if (i == -1)
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return (error);
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buf[i] = '\0';
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*pidptr = strtol(buf, &endptr, 10);
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if (endptr != &buf[i])
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return (EINVAL);
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return (0);
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}
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struct pidfh *
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pidfile_open(const char *path, mode_t mode, pid_t *pidptr)
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{
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struct pidfh *pfh;
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struct stat sb;
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int error, fd;
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pfh = malloc(sizeof(*pfh));
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if (pfh == NULL)
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return (NULL);
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if (path == NULL) {
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snprintf(pfh->pf_path, sizeof(pfh->pf_path), "/var/run/%s.pid",
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getprogname());
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} else {
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strlcpy(pfh->pf_path, path, sizeof(pfh->pf_path));
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}
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if (strlen(pfh->pf_path) == sizeof(pfh->pf_path) - 1) {
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free(pfh);
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errno = ENAMETOOLONG;
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return (NULL);
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}
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/*
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* Open the PID file and obtain exclusive lock.
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* We truncate PID file here only to remove old PID immediatelly,
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* PID file will be truncated again in pidfile_write(), so
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* pidfile_write() can be called multiple times.
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*/
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fd = open(pfh->pf_path,
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O_WRONLY | O_CREAT | O_EXLOCK | O_TRUNC | O_NONBLOCK, mode);
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if (fd == -1) {
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if (errno == EWOULDBLOCK && pidptr != NULL) {
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errno = pidfile_read(pfh->pf_path, pidptr);
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if (errno == 0)
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errno = EEXIST;
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}
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free(pfh);
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return (NULL);
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}
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/*
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* Remember file information, so in pidfile_write() we are sure we write
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* to the proper descriptor.
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*/
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if (fstat(fd, &sb) == -1) {
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error = errno;
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unlink(pfh->pf_path);
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close(fd);
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free(pfh);
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errno = error;
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return (NULL);
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}
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pfh->pf_fd = fd;
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pfh->pf_dev = sb.st_dev;
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pfh->pf_ino = sb.st_ino;
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return (pfh);
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}
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int
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pidfile_write(struct pidfh *pfh)
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{
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struct stat sb;
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char pidstr[16];
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int error, fd;
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/*
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* Check remembered descriptor, so we don't overwrite some other
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* file if pidfile was closed and descriptor reused.
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*/
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errno = pidfile_verify(pfh);
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if (errno != 0) {
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/*
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* Don't close descriptor, because we are not sure if it's ours.
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*/
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return (-1);
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}
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fd = pfh->pf_fd;
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/*
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* Truncate PID file, so multiple calls of pidfile_write() are allowed.
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*/
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if (ftruncate(fd, 0) == -1) {
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error = errno;
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_pidfile_remove(pfh, 0);
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errno = error;
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return (-1);
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}
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snprintf(pidstr, sizeof(pidstr), "%u", getpid());
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if (write(fd, pidstr, strlen(pidstr)) != (ssize_t)strlen(pidstr)) {
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error = errno;
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_pidfile_remove(pfh, 0);
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errno = error;
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return (-1);
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}
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return (0);
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}
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int
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pidfile_close(struct pidfh *pfh)
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{
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int error;
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error = pidfile_verify(pfh);
|
||||
if (error != 0) {
|
||||
errno = error;
|
||||
return (-1);
|
||||
}
|
||||
|
||||
if (close(pfh->pf_fd) == -1)
|
||||
error = errno;
|
||||
free(pfh);
|
||||
if (error != 0) {
|
||||
errno = error;
|
||||
return (-1);
|
||||
}
|
||||
return (0);
|
||||
}
|
||||
|
||||
static int
|
||||
_pidfile_remove(struct pidfh *pfh, int freeit)
|
||||
{
|
||||
int error;
|
||||
|
||||
error = pidfile_verify(pfh);
|
||||
if (error != 0) {
|
||||
errno = error;
|
||||
return (-1);
|
||||
}
|
||||
|
||||
if (unlink(pfh->pf_path) == -1)
|
||||
error = errno;
|
||||
if (flock(pfh->pf_fd, LOCK_UN) == -1) {
|
||||
if (error == 0)
|
||||
error = errno;
|
||||
}
|
||||
if (close(pfh->pf_fd) == -1) {
|
||||
if (error == 0)
|
||||
error = errno;
|
||||
}
|
||||
if (freeit)
|
||||
free(pfh);
|
||||
else
|
||||
pfh->pf_fd = -1;
|
||||
if (error != 0) {
|
||||
errno = error;
|
||||
return (-1);
|
||||
}
|
||||
return (0);
|
||||
}
|
||||
|
||||
int
|
||||
pidfile_remove(struct pidfh *pfh)
|
||||
{
|
||||
|
||||
return (_pidfile_remove(pfh, 1));
|
||||
}
|
Loading…
Reference in New Issue
Block a user