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.

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().