---
name: "tempnam"
section: "3p"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/tempnam/3p"
---

# tempnam(3p)

create a name for a temporary file

## 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 .