Section: POSIX Programmer's Manual (3P)
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
--- create a name for a temporary file
char *tempnam(const char *dir, const char *pfx);
function shall generate a pathname that may be used for a temporary
function allows the user to control the choice of a directory. The
argument points to the name of the directory in which the file is to be
is a null pointer or points to a string which is not a name for an
appropriate directory, the path prefix defined as P_tmpdir in the
header shall be used. If that directory is not accessible, an
implementation-defined directory may be used.
Many applications prefer their temporary files to have certain initial
letter sequences in their names. The
argument should be used for this. This argument may be a null pointer
or point to a string of up to five bytes to be used as the beginning of
Some implementations of
internally. On such implementations, if called more than
times in a single process, the behavior is implementation-defined.
Upon successful completion,
shall allocate space for a string, put the generated pathname in that
space, and return a pointer to it. The pointer shall be suitable for
use in a subsequent call to
Otherwise, it shall return a null pointer and set
to indicate the error.
function shall fail if:
Insufficient storage space is available.
The following sections are informative.
Generating a Pathname
The following example generates a pathname for a temporary file in
with the prefix
After the pathname has been created, the call to
deallocates the space used to store the pathname.
const char *directory = "/tmp";
const char *fileprefix = "file";
file = tempnam(directory, fileprefix);
This function only creates pathnames. It is the application's
responsibility to create and remove the files. Between the time a
pathname is created and the file is opened, it is possible for some
other process to create a file with the same name. Applications may
Applications should use the
functions instead of the obsolescent
function may be removed in a future version.
The Base Definitions volume of POSIX.1-2008,
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
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