I'm tired of seeing this done incorrectly and non-portably, so add a
flopen(3) function which reliably opens and locks a file. MFC after: 3 weeks
This commit is contained in:
Dag-Erling Smørgrav
parent
703ec91e6a
commit
9667055264
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=169446
@ -8,11 +8,11 @@ SHLIBDIR?= /lib
|
||||
LIB= util
|
||||
SHLIB_MAJOR= 6
|
||||
|
||||
SRCS= _secure_path.c auth.c fparseln.c humanize_number.c kld.c login.c \
|
||||
login_auth.c login_cap.c login_class.c login_crypt.c login_ok.c \
|
||||
login_times.c login_tty.c logout.c logwtmp.c \
|
||||
pidfile.c property.c pty.c pw_util.c realhostname.c stub.c \
|
||||
trimdomain.c uucplock.c
|
||||
SRCS= _secure_path.c auth.c flopen.c fparseln.c humanize_number.c \
|
||||
kld.c login.c login_auth.c login_cap.c login_class.c \
|
||||
login_crypt.c login_ok.c login_times.c login_tty.c logout.c \
|
||||
logwtmp.c pidfile.c property.c pty.c pw_util.c realhostname.c \
|
||||
stub.c trimdomain.c uucplock.c
|
||||
INCS= libutil.h login_cap.h
|
||||
|
||||
CFLAGS+= -DLIBC_SCCS
|
||||
@ -27,7 +27,7 @@ MAN+= kld.3 login.3 login_auth.3 login_tty.3 logout.3 logwtmp.3 pty.3 \
|
||||
login_cap.3 login_class.3 login_times.3 login_ok.3 \
|
||||
_secure_path.3 uucplock.3 property.3 auth.3 realhostname.3 \
|
||||
realhostname_sa.3 trimdomain.3 fparseln.3 humanize_number.3 \
|
||||
pidfile.3
|
||||
pidfile.3 flopen.3
|
||||
MAN+= login.conf.5 auth.conf.5
|
||||
MLINKS+= kld.3 kld_isloaded.3 kld.3 kld_load.3
|
||||
MLINKS+= property.3 properties_read.3 property.3 properties_free.3
|
||||
|
||||
79
lib/libutil/flopen.3
Normal file
79
lib/libutil/flopen.3
Normal file
@ -0,0 +1,79 @@
|
||||
.\"-
|
||||
.\" Copyright (c) 2007 Dag-Erling Coïdan Smørgrav
|
||||
.\" 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 AUTHOR 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 AUTHOR 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 May 10, 2007
|
||||
.Dt FLOPEN 3
|
||||
.Os
|
||||
.Sh NAME
|
||||
.Nm flopen
|
||||
.Nd "Reliably open and lock a file"
|
||||
.Sh LIBRARY
|
||||
.Lb libutil
|
||||
.Sh SYNOPSIS
|
||||
.In sys/fcntl.h
|
||||
.In libutil.h
|
||||
.Ft int
|
||||
.Fn flopen "const char *path" "int flags"
|
||||
.Ft int
|
||||
.Fn flopen "const char *path" "int flags" "mode_t mode"
|
||||
.Sh DESCRIPTION
|
||||
The
|
||||
.Fn flopen
|
||||
function opens or creates a file and acquires an exclusive lock on it.
|
||||
It is essentially equivalent with calling
|
||||
.Fn open
|
||||
with the same parameters followed by
|
||||
.Fn flock
|
||||
with an
|
||||
.Va operation
|
||||
argument of
|
||||
.Dv LOCK_EX ,
|
||||
except that
|
||||
.Fn flopen
|
||||
will attempt to detect and handle races that may occur between opening
|
||||
/ creating the file and locking it.
|
||||
Thus, it is well suited for opening lock files, PID files, spool
|
||||
files, mailboxes and other kinds of files which are used for
|
||||
synchronization between processes.
|
||||
.Pp
|
||||
As with
|
||||
.Fn flopen ,
|
||||
the additional
|
||||
.Va mode
|
||||
argument is required if
|
||||
.Va flags
|
||||
includes
|
||||
.Dv O_CREAT .
|
||||
.Sh SEE ALSO
|
||||
.Xr flock 2 ,
|
||||
.Xr open 2
|
||||
.Sh AUTHORS
|
||||
.An -nosplit
|
||||
The
|
||||
.Nm
|
||||
function and this manual page were written by
|
||||
.An Dag-Erling Sm\(/orgrav Aq des@FreeBSD.org .
|
||||
91
lib/libutil/flopen.c
Normal file
91
lib/libutil/flopen.c
Normal file
@ -0,0 +1,91 @@
|
||||
/*-
|
||||
* Copyright (c) 2007 Dag-Erling Coïdan Smørgrav
|
||||
* 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
|
||||
* in this position and unchanged.
|
||||
* 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 AUTHOR 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 AUTHOR 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.
|
||||
*
|
||||
* $Id$
|
||||
*/
|
||||
|
||||
#include <sys/cdefs.h>
|
||||
__FBSDID("$FreeBSD$");
|
||||
|
||||
#include <sys/stat.h>
|
||||
|
||||
#include <errno.h>
|
||||
#include <fcntl.h>
|
||||
#include <stdarg.h>
|
||||
|
||||
int
|
||||
flopen(const char *path, int flags, ...)
|
||||
{
|
||||
struct stat sb, fsb;
|
||||
mode_t mode;
|
||||
int fd, serrno;
|
||||
|
||||
#ifdef O_EXLOCK
|
||||
flags &= ~O_EXLOCK;
|
||||
#endif
|
||||
|
||||
if (flags & O_CREAT) {
|
||||
va_list ap;
|
||||
|
||||
va_start(ap, flags);
|
||||
mode = va_arg(ap, int); /* mode_t promoted to int */
|
||||
va_end(ap);
|
||||
} else {
|
||||
mode = 0;
|
||||
}
|
||||
|
||||
for (;;) {
|
||||
if ((fd = open(path, flags, mode)) == -1)
|
||||
/* non-existent or no access */
|
||||
return (-1);
|
||||
if (flock(fd, LOCK_EX) == -1) {
|
||||
/* unsupported or interrupted */
|
||||
serrno = errno;
|
||||
close(fd);
|
||||
errno = serrno;
|
||||
return (-1);
|
||||
}
|
||||
if (stat(path, &sb) == -1) {
|
||||
/* disappeared from under our feet */
|
||||
close(fd);
|
||||
continue;
|
||||
}
|
||||
if (fstat(fd, &fsb) == -1) {
|
||||
/* can't happen [tm] */
|
||||
serrno = errno;
|
||||
close(fd);
|
||||
errno = serrno;
|
||||
return (-1);
|
||||
}
|
||||
if (sb.st_dev != fsb.st_dev ||
|
||||
sb.st_ino != fsb.st_ino) {
|
||||
/* changed under our feet */
|
||||
close(fd);
|
||||
continue;
|
||||
}
|
||||
return (fd);
|
||||
}
|
||||
}
|
||||
@ -70,6 +70,7 @@ void clean_environment(const char * const *_white,
|
||||
const char * const *_more_white);
|
||||
int extattr_namespace_to_string(int _attrnamespace, char **_string);
|
||||
int extattr_string_to_namespace(const char *_string, int *_attrnamespace);
|
||||
int flopen(const char *_path, int _flags, mode_t _mode);
|
||||
void login(struct utmp *_ut);
|
||||
int login_tty(int _fd);
|
||||
int logout(const char *_line);
|
||||
|
||||
Loading…
Reference in New Issue
Block a user