1.\" Copyright (c) 1988, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" the American National Standards Committee X3, on Information 6.\" Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. All advertising materials mentioning features or use of this software 17.\" must display the following acknowledgement: 18.\" This product includes software developed by the University of 19.\" California, Berkeley and its contributors. 20.\" 4. Neither the name of the University nor the names of its contributors 21.\" may be used to endorse or promote products derived from this software 22.\" without specific prior written permission. 23.\" 24.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34.\" SUCH DAMAGE. 35.\" 36.\" @(#)tmpnam.3 8.2 (Berkeley) 11/17/93 37.\" $FreeBSD: src/lib/libc/stdio/tmpnam.3,v 1.5.2.5 2001/12/14 18:33:57 ru Exp $ 38.\" $DragonFly: src/lib/libc/stdio/tmpnam.3,v 1.3 2006/05/26 19:39:37 swildner Exp $ 39.\" 40.Dd November 17, 1993 41.Dt TMPFILE 3 42.Os 43.Sh NAME 44.Nm tempnam , 45.Nm tmpfile , 46.Nm tmpnam 47.Nd temporary file routines 48.Sh LIBRARY 49.Lb libc 50.Sh SYNOPSIS 51.In stdio.h 52.Ft FILE * 53.Fn tmpfile void 54.Ft char * 55.Fn tmpnam "char *str" 56.Ft char * 57.Fn tempnam "const char *tmpdir" "const char *prefix" 58.Sh DESCRIPTION 59The 60.Fn tmpfile 61function 62returns a pointer to a stream associated with a file descriptor returned 63by the routine 64.Xr mkstemp 3 . 65The created file is unlinked before 66.Fn tmpfile 67returns, causing the file to be automatically deleted when the last 68reference to it is closed. 69The file is opened with the access value 70.Ql w+ . 71The file is created in the directory determined by the environment variable 72.Ev TMPDIR 73if set. 74The default location if 75.Ev TMPDIR 76is not set is 77.Pa /tmp . 78.Pp 79The 80.Fn tmpnam 81function 82returns a pointer to a file name, in the 83.Dv P_tmpdir 84directory, which 85did not reference an existing file at some indeterminate point in the 86past. 87.Dv P_tmpdir 88is defined in the include file 89.In stdio.h . 90If the argument 91.Fa str 92is 93.Pf non- Dv NULL , 94the file name is copied to the buffer it references. 95Otherwise, the file name is copied to a static buffer. 96In either case, 97.Fn tmpnam 98returns a pointer to the file name. 99.Pp 100The buffer referenced by 101.Fa str 102is expected to be at least 103.Dv L_tmpnam 104bytes in length. 105.Dv L_tmpnam 106is defined in the include file 107.In stdio.h . 108.Pp 109The 110.Fn tempnam 111function 112is similar to 113.Fn tmpnam , 114but provides the ability to specify the directory which will 115contain the temporary file and the file name prefix. 116.Pp 117The environment variable 118.Ev TMPDIR 119(if set), the argument 120.Fa tmpdir 121(if 122.Pf non- Dv NULL ) , 123the directory 124.Dv P_tmpdir , 125and the directory 126.Pa /tmp 127are tried, in the listed order, as directories in which to store the 128temporary file. 129.Pp 130The argument 131.Fa prefix , 132if 133.Pf non- Dv NULL , 134is used to specify a file name prefix, which will be the 135first part of the created file name. 136.Fn Tempnam 137allocates memory in which to store the file name; the returned pointer 138may be used as a subsequent argument to 139.Xr free 3 . 140.Sh RETURN VALUES 141The 142.Fn tmpfile 143function 144returns a pointer to an open file stream on success, and a 145.Dv NULL 146pointer 147on error. 148.Pp 149The 150.Fn tmpnam 151and 152.Fn tempfile 153functions 154return a pointer to a file name on success, and a 155.Dv NULL 156pointer 157on error. 158.Sh ERRORS 159The 160.Fn tmpfile 161function 162may fail and set the global variable 163.Va errno 164for any of the errors specified for the library functions 165.Xr fdopen 3 166or 167.Xr mkstemp 3 . 168.Pp 169The 170.Fn tmpnam 171function 172may fail and set 173.Va errno 174for any of the errors specified for the library function 175.Xr mktemp 3 . 176.Pp 177The 178.Fn tempnam 179function 180may fail and set 181.Va errno 182for any of the errors specified for the library functions 183.Xr malloc 3 184or 185.Xr mktemp 3 . 186.Sh SEE ALSO 187.Xr mkstemp 3 , 188.Xr mktemp 3 189.Sh STANDARDS 190The 191.Fn tmpfile 192and 193.Fn tmpnam 194functions 195conform to 196.St -isoC . 197.Sh BUGS 198These interfaces are provided for System V and 199.Tn ANSI 200compatibility only. 201The 202.Xr mkstemp 3 203interface is strongly preferred. 204.Pp 205There are four important problems with these interfaces (as well as 206with the historic 207.Xr mktemp 3 208interface). 209First, there is an obvious race between file name selection and file 210creation and deletion. 211Second, most historic implementations provide only a limited number 212of possible temporary file names (usually 26) before file names will 213start being recycled. 214Third, the System V implementations of these functions (and of 215.Xr mktemp 3 ) 216use the 217.Xr access 2 218function to determine whether or not the temporary file may be created. 219This has obvious ramifications for setuid or setgid programs, complicating 220the portable use of these interfaces in such programs. 221Finally, there is no specification of the permissions with which the 222temporary files are created. 223.Pp 224This implementation does not have these flaws, but portable software 225cannot depend on that. 226In particular, the 227.Fn tmpfile 228interface should not be used in software expected to be used on other systems 229if there is any possibility that the user does not wish the temporary file to 230be publicly readable and writable. 231