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126 lines
3.3 KiB
Groff
126 lines
3.3 KiB
Groff
.\"-
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.\" Copyright (c) 2007 Dag-Erling Smørgrav
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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 AUTHOR 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 AUTHOR 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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.Dd July 28, 2017
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.Dt FLOPEN 3
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.Os
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.Sh NAME
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.Nm flopen ,
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.Nm flopenat
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.Nd "Reliably open and lock a file"
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.Sh LIBRARY
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.Lb libutil
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.Sh SYNOPSIS
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.In sys/fcntl.h
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.In libutil.h
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.Ft int
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.Fn flopen "const char *path" "int flags"
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.Ft int
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.Fn flopen "const char *path" "int flags" "mode_t mode"
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.Ft int
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.Fn flopenat "int fd" "const char *path" "int flags"
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.Ft int
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.Fn flopenat "int fd" "const char *path" "int flags" "mode_t mode"
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.Sh DESCRIPTION
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The
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.Fn flopen
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function opens or creates a file and acquires an exclusive lock on it.
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It is essentially equivalent with calling
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.Fn open
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with the same parameters followed by
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.Fn flock
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with an
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.Fa operation
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argument of
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.Dv LOCK_EX ,
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except that
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.Fn flopen
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will attempt to detect and handle races that may occur between opening
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/ creating the file and locking it.
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Thus, it is well suited for opening lock files, PID files, spool
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files, mailboxes and other kinds of files which are used for
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synchronization between processes.
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.Pp
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If
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.Fa flags
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includes
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.Dv O_NONBLOCK
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and the file is already locked,
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.Fn flopen
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will fail and set
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.Va errno
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to
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.Dv EWOULDBLOCK .
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.Pp
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As with
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.Fn open ,
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the additional
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.Fa mode
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argument is required if
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.Fa flags
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includes
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.Dv O_CREAT .
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.Pp
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The
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.Fn flopenat
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function is equivalent to the
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.Fn flopen
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function except in the case where the
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.Fa path
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specifies a relative path.
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In this case the file to be opened is determined relative to the directory
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associated with the file descriptor
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.Fa fd
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instead of the current working directory.
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If
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.Fn flopenat
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is passed the special value
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.Dv AT_FDCWD
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in the
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.Fa fd
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parameter, the current working directory is used
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and the behavior is identical to a call to
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.Fn flopen .
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.Sh RETURN VALUES
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If successful,
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.Fn flopen
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returns a valid file descriptor.
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Otherwise, it returns -1, and sets
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.Va errno
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as described in
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.Xr flock 2
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and
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.Xr open 2 .
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.Sh SEE ALSO
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.Xr errno 2 ,
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.Xr flock 2 ,
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.Xr open 2
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.Sh AUTHORS
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.An -nosplit
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The
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.Nm
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function and this manual page were written by
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.An Dag-Erling Sm\(/orgrav Aq Mt des@FreeBSD.org .
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