The Open Group Base Specifications Issue 6
IEEE Std 1003.1, 2004 Edition
Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.

#### NAME

> tmpnam - create a name for a temporary file

#### SYNOPSIS

> ``#include <stdio.h>
> char *tmpnam(char *`s`);
> ``

#### DESCRIPTION

> [CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to the ISO C standard.

> The tmpnam() function shall generate a string that is a valid filename and that is not the same as the name of an existing file. The function is potentially capable of generating {TMP_MAX} different strings, but any or all of them may already be in use by existing files and thus not be suitable return values.

> The tmpnam() function generates a different string each time it is called from the same process, up to {TMP_MAX} times. If it is called more than {TMP_MAX} times, the behavior is implementation-defined.

> The implementation shall behave as if no function defined in this volume of IEEE Std 1003.1-2001, except tempnam(), calls tmpnam().

> [CX] If the application uses any of the functions guaranteed to be available if either _POSIX_THREAD_SAFE_FUNCTIONS or _POSIX_THREADS is defined, the application shall ensure that the tmpnam() function is called with a non-NULL parameter.

#### RETURN VALUE

> Upon successful completion, tmpnam() shall return a pointer to a string. If no suitable string can be generated, the tmpnam() function shall return a null pointer.

> If the argument s is a null pointer, tmpnam() shall leave its result in an internal static object and return a pointer to that object. Subsequent calls to tmpnam() may modify the same object. If the argument s is not a null pointer, it is presumed to point to an array of at least L_tmpnam chars; tmpnam() shall write its result in that array and shall return the argument as its value.

#### ERRORS

> No errors are defined.

The following sections are informative.

#### EXAMPLES

> ##### Generating a Filename

> The following example generates a unique filename and stores it in the array pointed to by ptr.

>     #include <stdio.h>
>     ...
>     char filename[L_tmpnam+1];
>     char *ptr;

>     ptr = tmpnam(filename);

#### APPLICATION USAGE

> This function only creates filenames. 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.

#### RATIONALE

> None.

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> fopen(), open(), tempnam(), tmpfile(), unlink(), the Base Definitions volume of IEEE Std 1003.1-2001, <stdio.h>

#### CHANGE HISTORY

> First released in Issue 1. Derived from Issue 1 of the SVID.

#### Issue 5

> The DESCRIPTION is updated for alignment with the POSIX Threads Extension.

#### Issue 6

> Extensions beyond the ISO C standard are marked.

> The DESCRIPTION is updated to avoid use of the term "must" for application requirements.

> The DESCRIPTION is expanded for alignment with the ISO/IEC 9899:1999 standard.

> IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/142 is applied, updating the DESCRIPTION to allow implementations of the tempnam() function to call tmpnam().

End of informative text.

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