.\" Copyright (c) 1988, 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" This code is derived from software contributed to Berkeley by .\" the American National Standards Committee X3, on Information .\" Processing Systems. .\" .\" 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. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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. .\" .\" @(#)tmpnam.3 8.2 (Berkeley) 11/17/93 .\" $FreeBSD: src/lib/libc/stdio/tmpnam.3,v 1.20 2007/03/16 21:46:24 maxim Exp $ .\" .Dd November 12, 2008 .Dt TMPFILE 3 .Os .Sh NAME .Nm tempnam , .Nm tmpfile , .Nm tmpnam .Nd temporary file routines .Sh LIBRARY .Lb libc .Sh SYNOPSIS .In stdio.h .Ft FILE * .Fo tmpfile .Fa "void" .Fc .Ft char * .Fo tmpnam .Fa "char *s" .Fc .Ft char * .Fo tempnam .Fa "const char *dir" .Fa "const char *pfx" .Fc .Sh DESCRIPTION The .Fn tmpfile function returns a pointer to a stream associated with a file descriptor returned by the routine .Xr mkstemp 3 . The created file is unlinked before .Fn tmpfile returns, causing the file to be automatically deleted when the last reference to it is closed. The file is opened with the access value .Ql w+ . If the environment variable .Ev TMPDIR is defined, the file is created in the specified directory. The default location, if .Ev TMPDIR is not set, is .Pa /tmp . .Pp The .Fn tmpnam function returns a pointer to a file name, in the .Dv P_tmpdir directory, which did not reference an existing file at some indeterminate point in the past. .Dv P_tmpdir is defined in the include file .In stdio.h . If the argument .Fa s is .Pf non- Dv NULL , the file name is copied to the buffer it references. Otherwise, the file name is copied to a static buffer. In either case, .Fn tmpnam returns a pointer to the file name. .Pp The buffer referenced by .Fa s is expected to be at least .Dv L_tmpnam bytes in length. .Dv L_tmpnam is defined in the include file .In stdio.h . .Pp The .Fn tempnam function is similar to .Fn tmpnam , but provides the ability to specify the directory which will contain the temporary file and the file name prefix. .Pp The argument .Fa dir (if .Pf non- Dv NULL ) , the directory .Dv P_tmpdir , the environment variable .Ev TMPDIR (if set), the directory .Pa /tmp and finally, the current directory, are tried, in the listed order, as directories in which to store the temporary file. .Pp The argument .Fa pfx , if .Pf non- Dv NULL , is used to specify a file name prefix, which will be the first part of the created file name. The .Fn tempnam function allocates memory in which to store the file name; the returned pointer may be used as a subsequent argument to .Xr free 3 . .Sh RETURN VALUES The .Fn tmpfile function returns a pointer to an open file stream on success, and a .Dv NULL pointer on error. .Pp The .Fn tmpnam and .Fn tempfile functions return a pointer to a file name on success, and a .Dv NULL pointer on error. .Sh ENVIRONMENT .Bl -tag -width Ds .It Ev TMPDIR .Pf [ Fn tempnam only] If set, the directory in which the temporary file is stored. .Ev TMPDIR is ignored for processes for which .Xr issetugid 2 is true. .El .Sh COMPATIBILITY These interfaces are provided from System V and .Tn ANSI compatibility only. .Pp Most historic implementations of these functions provide only a limited number of possible temporary file names (usually 26) before file names will start being recycled. System V implementations of these functions (and of .Xr mktemp 3 ) use the .Xr access 2 system call to determine whether or not the temporary file may be created. This has obvious ramifications for setuid or setgid programs, complicating the portable use of these interfaces in such programs. .Pp The .Fn tmpfile interface should not be used in software expected to be used on other systems if there is any possibility that the user does not wish the temporary file to be publicly readable and writable. .Sh ERRORS The .Fn tmpfile function may fail and set the global variable .Va errno for any of the errors specified for the library functions .Xr fdopen 3 or .Xr mkstemp 3 . .Pp The .Fn tmpnam function may fail and set .Va errno for any of the errors specified for the library function .Xr mktemp 3 . .Pp The .Fn tempnam function may fail and set .Va errno for any of the errors specified for the library functions .Xr malloc 3 or .Xr mktemp 3 . .Sh SECURITY CONSIDERATIONS The .Fn tmpnam and .Fn tempnam functions are susceptible to a race condition occurring between the selection of the file name and the creation of the file, which allows malicious users to potentially overwrite arbitrary files in the system, depending on the level of privilege of the running program. Additionally, there is no means by which file permissions may be specified. It is strongly suggested that .Xr mkstemp 3 be used in place of these functions. (See the FSA.) .Sh LEGACY DESCRIPTION In legacy mode, the order directories are tried by the .Fn tempnam function is different; the environment variable .Ev TMPDIR (if defined) is used first. .Sh SEE ALSO .Xr mkstemp 3 , .Xr mktemp 3 .Sh STANDARDS The .Fn tmpfile and .Fn tmpnam functions conform to .St -isoC .