| TMPFILE(3) | Library Functions Manual | TMPFILE(3) |
tempnam, tmpfile,
tmpnam — temporary file
routines
Standard C Library (libc, -lc)
#include
<stdio.h>
FILE *
tmpfile(void);
char *
tmpnam(char *s);
char *
tempnam(const char *dir,
const char *pfx);
The
tmpfile()
function returns a pointer to a stream associated with a file descriptor
returned by the routine mkstemp(3). The created file is
unlinked before 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
‘w+’. If the environment variable
TMPDIR is defined, the file is created in the
specified directory. The default location, if TMPDIR
is not set, is /tmp.
The
tmpnam()
function returns a pointer to a file name, in the
P_tmpdir directory, which did not reference an
existing file at some indeterminate point in the past.
P_tmpdir is defined in the include file
<stdio.h>. If the argument
s is non-NULL, the file name
is copied to the buffer it references. Otherwise, the file name is copied to
a static buffer. In either case, tmpnam() returns a
pointer to the file name.
The buffer referenced by s is expected to be
at least L_tmpnam bytes in length.
L_tmpnam is defined in the include file
<stdio.h>.
The
tempnam()
function is similar to tmpnam(), but provides the
ability to specify the directory which will contain the temporary file and
the file name prefix.
The argument dir (if
non-NULL), the directory
P_tmpdir, the environment variable
TMPDIR (if set), the directory
/tmp and finally, the current directory, are tried,
in the listed order, as directories in which to store the temporary
file.
The argument pfx, if
non-NULL, is used to specify a file name prefix,
which will be the first part of the created file name. The
tempnam()
function allocates memory in which to store the file name; the returned
pointer may be used as a subsequent argument to
free(3).
The tmpfile() function returns a pointer
to an open file stream on success, and a NULL
pointer on error.
The tmpnam() and
tempfile() functions return a pointer to a file name
on success, and a NULL pointer on error.
TMPDIRtempnam() only] If set, the directory in which
the temporary file is stored. TMPDIR is ignored
for processes for which issetugid(2) is true.These interfaces are provided from System V and ANSI compatibility only.
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 mktemp(3)) use the 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.
The 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.
The tmpfile() function may fail and set
the global variable errno for any of the errors
specified for the library functions fdopen(3) or
mkstemp(3).
The tmpnam() function may fail and set
errno for any of the errors specified for the library
function mktemp(3).
The tempnam() function may fail and set
errno for any of the errors specified for the library
functions malloc(3) or mktemp(3).
The tmpnam() and
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 mkstemp(3) be
used in place of these functions. (See the FSA.)
In legacy mode, the order directories are tried by the
tempnam()
function is different; the environment variable
TMPDIR (if defined) is used first.
The tmpfile() and
tmpnam() functions conform to
ISO/IEC 9899:1990
(“ISO C90”).
| November 12, 2008 | Mac OS X 12 |