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155 lines
4.6 KiB
Groff
155 lines
4.6 KiB
Groff
.\" Copyright (c) 1989, 1991, 1993
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.\" The Regents of the University of California. 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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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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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.\" @(#)mktemp.3 8.1 (Berkeley) 6/4/93
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.\"
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.TH MKTEMP 3 "27 January 1997" GNO "Library Routines"
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.SH NAME
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.BR mktemp
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\- make temporary file name (unique)
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.SH SYNOPSIS
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#include <unistd.h>
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.sp 1
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char *
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\fBmktemp\fR (char *\fItemplate\fR);
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.br
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int
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\fBmkstemp\fR (char *\fItemplate\fR);
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.SH DESCRIPTION
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The
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.BR mktemp
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function
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takes the given file name template and overwrites a portion of it
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to create a file name.
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This file name is unique and suitable for use
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by the application.
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The template may be any file name with some number of
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.IR X \'s
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appended
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to it, for example \fB/tmp/temp.\fIXXXX\fR.
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The trailing
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.IR X \'s
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are replaced with the current process number and/or a
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unique letter combination.
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The number of unique file names
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.BR mktemp
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can return depends on the number of
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.IR X \'s
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provided; six
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.IR X \'s
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will
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result in
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.BR mktemp
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testing roughly 26 ** 6 combinations.
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.LP
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The
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.BR mkstemp
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function
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makes the same replacement to the template and creates the template file,
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mode 0600, returning a file descriptor opened for reading and writing.
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This avoids the race between testing for a file's existence and opening it
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for use.
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.SH RETURN VALUES
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The
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.BR mktemp
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function
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returns a pointer to the template on success and
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.BR NULL
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on failure.
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The
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.BR mkstemp
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function
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returns \-1 if no suitable file could be created.
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If either call fails an error code is placed in the global variable
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.IR errno .
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.SH ERRORS
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The
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.BR mktemp
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and
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.BR mkstemp
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functions
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may set
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.IR errno
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to one of the following values:
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.RS
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.IP \fBENOTDIR\fR
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The pathname portion of the template is not an existing directory.
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.RE
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.LP
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The
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.BR mktemp
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and
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.BR mkstemp
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functions
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may also set
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.IR errno
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to any value specified by the
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.BR stat (2)
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function.
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.LP
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The
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.BR mkstemp
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function
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may also set
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.IR errno
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to any value specified by the
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.BR open (2)
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function.
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.SH NOTES
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A common problem that results in a core dump on many architectures
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is that the programmer passes in a read-only string to
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.BR mktemp
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or
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.BR mkstemp .
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This is common with programs that were developed before
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ANSI/C compilers were common.
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For example, calling
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.BR mkstemp
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with an argument of \fB/tmp/tempfile.\fIXXXXXX\fR
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will result in a core dump due to
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.BR mkstemp
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attempting to modify the string constant that was given.
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If the program in question makes heavy use of that type
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of function call, some compilers have the option of compiling the program
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so that it will store string constants in a writable segment of memory
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(in the data rather than the text segment). While it is good programming
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practise to avoid this problem, it is not strictly necessary under GNO
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due to the lack of a write-only text segment.
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.SH SEE ALSO
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.BR chmod (2),
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.BR getpid (2),
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.BR open (2),
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.BR stat (2)
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.SH HISTORY
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A
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.BR mktemp
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function appeared in Version 7 AT&T UNIX.
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