[apple/libc.git] / stdio / tmpnam.3

.\" 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.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 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 1.10 2001/10/01 16:08:59 ru Exp $
.\"
.Dd November 17, 1993
.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 *
.Fn tmpfile void
.Ft char *
.Fn tmpnam "char *str"
.Ft char *
.Fn tempnam "const char *tmpdir" "const char *prefix"
.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+ .
The file is created in the directory determined by the environment variable
.Ev TMPDIR
if set.
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
.Aq Pa stdio.h .
If the argument
.Fa str
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 str
is expected to be at least
.Dv L_tmpnam
bytes in length.
.Dv L_tmpnam
is defined in the include file
.Aq Pa 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 environment variable
.Ev TMPDIR
(if set), the argument
.Fa tmpdir
(if
.Pf non- Dv NULL ) ,
the directory
.Dv P_tmpdir ,
and the directory
.Pa /tmp
are tried, in the listed order, as directories in which to store the
temporary file.
.Pp
The argument
.Fa prefix ,
if
.Pf non- Dv NULL ,
is used to specify a file name prefix, which will be the
first part of the created file name.
.Fn Tempnam
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 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 SEE ALSO
.Xr mkstemp 3 ,
.Xr mktemp 3
.Sh STANDARDS
The
.Fn tmpfile
and
.Fn tmpnam
functions
conform to
.St -isoC .
.Sh BUGS
These interfaces are provided for System V and
.Tn ANSI
compatibility only.
The
.Xr mkstemp 3
interface is strongly preferred.
.Pp
There are four important problems with these interfaces (as well as
with the historic
.Xr mktemp 3
interface).
First, there is an obvious race between file name selection and file
creation and deletion.
Second, most historic implementations provide only a limited number
of possible temporary file names (usually 26) before file names will
start being recycled.
Third, the System V implementations of these functions (and of
.Xr mktemp 3 )
use the
.Xr access 2
function 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.
Finally, there is no specification of the permissions with which the
temporary files are created.
.Pp
This implementation does not have these flaws, but portable software
cannot depend on that.
In particular, 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.
Commit	Line	Data
5b2abdfb A	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 1.10 2001/10/01 16:08:59 ru Exp $
	38	.\"
	39	.Dd November 17, 1993
	40	.Dt TMPFILE 3
	41	.Os
	42	.Sh NAME
	43	.Nm tempnam ,
	44	.Nm tmpfile ,
	45	.Nm tmpnam
	46	.Nd temporary file routines
	47	.Sh LIBRARY
	48	.Lb libc
	49	.Sh SYNOPSIS
	50	.In stdio.h
	51	.Ft FILE *
	52	.Fn tmpfile void
	53	.Ft char *
	54	.Fn tmpnam "char *str"
	55	.Ft char *
	56	.Fn tempnam "const char tmpdir" "const char prefix"
	57	.Sh DESCRIPTION
	58	The
	59	.Fn tmpfile
	60	function
	61	returns a pointer to a stream associated with a file descriptor returned
	62	by the routine
	63	.Xr mkstemp 3 .
	64	The created file is unlinked before
65	.Fn tmpfile
66	returns, causing the file to be automatically deleted when the last
67	reference to it is closed.
68	The file is opened with the access value
69	.Ql w+ .
70	The file is created in the directory determined by the environment variable
71	.Ev TMPDIR
72	if set.
73	The default location if
74	.Ev TMPDIR
75	is not set is
76	.Pa /tmp .
77	.Pp
78	The
79	.Fn tmpnam
80	function
81	returns a pointer to a file name, in the
82	.Dv P_tmpdir
83	directory, which
84	did not reference an existing file at some indeterminate point in the
85	past.
86	.Dv P_tmpdir
87	is defined in the include file
88	.Aq Pa stdio.h .
89	If the argument
90	.Fa str
91	is
92	.Pf non- Dv NULL ,
93	the file name is copied to the buffer it references.
94	Otherwise, the file name is copied to a static buffer.
95	In either case,
96	.Fn tmpnam
97	returns a pointer to the file name.
98	.Pp
99	The buffer referenced by
100	.Fa str
101	is expected to be at least
102	.Dv L_tmpnam
103	bytes in length.
104	.Dv L_tmpnam
105	is defined in the include file
106	.Aq Pa stdio.h .
107	.Pp
108	The
109	.Fn tempnam
110	function
111	is similar to
112	.Fn tmpnam ,
113	but provides the ability to specify the directory which will
114	contain the temporary file and the file name prefix.
115	.Pp
116	The environment variable
117	.Ev TMPDIR
118	(if set), the argument
119	.Fa tmpdir
120	(if
121	.Pf non- Dv NULL ) ,
122	the directory
123	.Dv P_tmpdir ,
124	and the directory
125	.Pa /tmp
126	are tried, in the listed order, as directories in which to store the
127	temporary file.
128	.Pp
129	The argument
130	.Fa prefix ,
131	if
132	.Pf non- Dv NULL ,
133	is used to specify a file name prefix, which will be the
134	first part of the created file name.
135	.Fn Tempnam
136	allocates memory in which to store the file name; the returned pointer
137	may be used as a subsequent argument to
138	.Xr free 3 .
139	.Sh RETURN VALUES
140	The
141	.Fn tmpfile
142	function
143	returns a pointer to an open file stream on success, and a
144	.Dv NULL
145	pointer
146	on error.
147	.Pp
148	The
149	.Fn tmpnam
150	and
151	.Fn tempfile
152	functions
153	return a pointer to a file name on success, and a
154	.Dv NULL
155	pointer
156	on error.
157	.Sh ERRORS
158	The
159	.Fn tmpfile
160	function
161	may fail and set the global variable
162	.Va errno
163	for any of the errors specified for the library functions
164	.Xr fdopen 3
165	or
166	.Xr mkstemp 3 .
167	.Pp
168	The
169	.Fn tmpnam
170	function
171	may fail and set
172	.Va errno
173	for any of the errors specified for the library function
174	.Xr mktemp 3 .
175	.Pp
176	The
177	.Fn tempnam
178	function
179	may fail and set
180	.Va errno
181	for any of the errors specified for the library functions
182	.Xr malloc 3
183	or
184	.Xr mktemp 3 .
185	.Sh SEE ALSO
186	.Xr mkstemp 3 ,
187	.Xr mktemp 3
188	.Sh STANDARDS
189	The
190	.Fn tmpfile
191	and
192	.Fn tmpnam
193	functions
194	conform to
195	.St -isoC .
196	.Sh BUGS
197	These interfaces are provided for System V and
198	.Tn ANSI
199	compatibility only.
200	The
201	.Xr mkstemp 3
202	interface is strongly preferred.
203	.Pp
204	There are four important problems with these interfaces (as well as
205	with the historic
206	.Xr mktemp 3
207	interface).
208	First, there is an obvious race between file name selection and file
209	creation and deletion.
210	Second, most historic implementations provide only a limited number
211	of possible temporary file names (usually 26) before file names will
212	start being recycled.
213	Third, the System V implementations of these functions (and of
214	.Xr mktemp 3 )
215	use the
216	.Xr access 2
217	function to determine whether or not the temporary file may be created.
218	This has obvious ramifications for setuid or setgid programs, complicating
219	the portable use of these interfaces in such programs.
220	Finally, there is no specification of the permissions with which the
221	temporary files are created.
222	.Pp
223	This implementation does not have these flaws, but portable software
224	cannot depend on that.
225	In particular, the
226	.Fn tmpfile
227	interface should not be used in software expected to be used on other systems
228	if there is any possibility that the user does not wish the temporary file to
229	be publicly readable and writable.