TEMPNAM(3P)

PROLOG
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.

NAME
tempnam — create a name for a temporary file

SYNOPSIS

#include <stdio.h>

char *tempnam(const char *dir, const char *pfx);

DESCRIPTION
The tempnam() function shall generate a pathname that may be used for a temporary file.

The tempnam() function allows the user to control the choice of a directory. The dir argument points to the name of the directory in which the file is to be created. If dir 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 <stdio.h> 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 pfx 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 the filename.

Some implementations of tempnam() may use tmpnam() internally. On such implementations, if called more than {TMP_MAX} times in a single process, the behavior is implementation-defined.

RETURN VALUE
Upon successful completion, tempnam() 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 free(). Otherwise, it shall return a null pointer and set errno to indicate the error.

ERRORS
The tempnam() function shall fail if:

ENOMEM
    Insufficient storage space is available.

The following sections are informative.

EXAMPLES

  Generating a Pathname

The following example generates a pathname for a temporary file in directory /tmp, with the prefix file. After the pathname has been created, the call to free() deallocates the space used to store the pathname.

    #include <stdio.h>
    #include <stdlib.h>
    ...
    const char *directory = "/tmp";
    const char *fileprefix = "file";
    char *file;

    file = tempnam(directory, fileprefix);
    free(file);

APPLICATION USAGE
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 find tmpfile() more useful.

Applications should use the tmpfile(), mkdtemp(), or mkstemp() functions instead of the obsolescent tempnam() function.

RATIONALE
None.

FUTURE DIRECTIONS
The tempnam() function may be removed in a future version.

SEE ALSO
fopen(), free(), mkdtemp(), open(), tmpfile(), tmpnam(), unlink()

The Base Definitions volume of POSIX.1-2017, <stdio.h>

COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. 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 http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .