Provided by: manpages-dev_2.17-1_all
tempnam - create a name for a temporary file
char *tempnam(const char *dir, const char *pfx);
The tempnam() function returns a pointer to a string that is a valid
filename, and such that a file with this name did not exist when
tempnam() checked. The filename suffix of the pathname generated will
start with pfx in case pfx is a non-NULL string of at most five bytes.
The directory prefix part of the pathname generated is required to be
‘appropriate’ (often that at least implies writable). Attempts to find
an appropriate directory go through the following steps: (i) In case
the environment variable TMPDIR exists and contains the name of an
appropriate directory, that is used. (ii) Otherwise, if the dir
argument is non-NULL and appropriate, it is used. (iii) Otherwise,
P_tmpdir (as defined in <stdio.h>) is used when appropriate. (iv)
Finally an implementation-defined directory may be used.
The tempnam() function returns a pointer to a unique temporary
filename, or NULL if a unique name cannot be generated.
ENOMEM Allocation of storage failed.
SUSv2 does not mention the use of TMPDIR; glibc will use it only when
the program is not set-user-ID. SVID2 specifies that the directory
used under (iv) is /tmp. SVID2 specifies that the string returned by
tempnam() was allocated using malloc(3) and hence can be freed by
The tempnam() function generates a different string each time it is
called, up to TMP_MAX (defined in <stdio.h>) times. If it is called
more than TMP_MAX times, the behaviour is implementation defined.
In case the pfx argument has length larger than five, glibc will use
the first five bytes. Upon failure to find a unique name, glibc will
The precise meaning of ‘appropriate’ is undefined; it is unspecified
how accessibility of a directory is determined. Never use this
function. Use mkstemp(3) instead.
SVID 2, 4.3BSD, POSIX 1003.1-2003
mkstemp(3), mktemp(3), tmpfile(3), tmpnam(3)