|TEMPNAM(3)||Linux Programmer's Manual||TEMPNAM(3)|
char *tempnam(const char *dir, const char *pfx);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
tempnam(): Since glibc 2.19: _DEFAULT_SOURCE Glibc 2.19 and earlier: _BSD_SOURCE || _SVID_SOURCE
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:
- In case the environment variable TMPDIR exists and contains the name of an appropriate directory, that is used.
- Otherwise, if the dir argument is non-NULL and appropriate, it is used.
- Otherwise, P_tmpdir (as defined in <stdio.h>) is used when appropriate.
- Finally an implementation-defined directory may be used.
- Allocation of storage failed.
|tempnam ()||Thread safety||MT-Safe env|
SUSv2 does not mention the use of TMPDIR; glibc will use it only when the program is not set-user-ID. On SVr4, the directory used under d) is /tmp (and this is what glibc does).
Because it dynamically allocates memory used to return the pathname, tempnam() is reentrant, and thus thread safe, unlike tmpnam(3).
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 behavior is implementation defined.
tempnam() uses at most the first five bytes from pfx.
The glibc implementation of tempnam() fails with the error EEXIST upon failure to find a unique name.