NAME

mkstemp - make a unique filename

SYNOPSIS

[XSI] #include <stdlib.h>

int mkstemp(char *template);

DESCRIPTION

The mkstemp() function shall replace the contents of the string pointed to by template by a unique filename, and return a file descriptor for the file open for reading and writing. The function thus prevents any possible race condition between testing whether the file exists and opening it for use. The string in template should look like a filename with six trailing 'X' s; mkstemp() replaces each 'X' with a character from the portable filename character set. The characters are chosen such that the resulting name does not duplicate the name of an existing file at the time of a call to mkstemp().

RETURN VALUE

Upon successful completion, mkstemp() shall return an open file descriptor. Otherwise, -1 shall be returned if no suitable file could be created.

ERRORS

No errors are defined.

EXAMPLES

Generating a Filename

The following example creates a file with a 10-character name beginning with the characters "file" and opens the file for reading and writing. The value returned as the value of fd is a file descriptor that identifies the file.

#include <stdlib.h>
...
char template[] = "/tmp/fileXXXXXX";
int fd;


fd = mkstemp(template);

APPLICATION USAGE

It is possible to run out of letters.

The mkstemp() function need not check to determine whether the filename part of template exceeds the maximum allowable filename length.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

getpid() , open() , tmpfile() , tmpnam() , the Base Definitions volume of IEEE Std 1003.1-2001, <stdlib.h>

CHANGE HISTORY

First released in Issue 4, Version 2.

Issue 5

Moved from X/OPEN UNIX extension to BASE.