MKTEMP(3)

NAME
mktemp, mkstemp, mkdtemp - make unique temporary file or directory name

LIBRARY
libc

SYNOPSIS
#include <stdlib.h>
char *
mktemp(char *template);
int
mkstemp(char *template);
char *
mkdtemp(char *template);

DESCRIPTION
The mktemp() function takes the given file name template and overwrites a portion of it to create a file name. This file name is unique and suitable for use by the application. The template may be any file name with some number of ‘Xs’ appended to it, for example /tmp/temp.XXXX. The trailing ‘Xs’ are replaced with the current process number and/or a unique letter combination. The number of unique file names mktemp() can return depends on the number of ‘Xs’ provided; six ‘Xs’ will result in mktemp() testing roughly 26 ** 6 combinations.

The mkstemp() function makes the same replacement to the template and creates the template file, mode 0600, returning a file descriptor opened for reading and writing. This avoids the race between testing for a file's existence and opening it for use.

The mkdtemp() function is similar to mkstemp(), but it creates a mode 0700 directory instead and returns the path.

RETURN VALUES
The mktemp() and mkdtemp() functions return a pointer to the template on success and NULL on failure. The mkstemp() function returns -1 if no suitable file could be created. If either call fails an error code is placed in the global variable errno.

ERRORS
The mktemp(), mkstemp() and mkdtemp() functions may set errno to one of the following values:

[ENOTDIR]
    The pathname portion of the template is not an existing directory.

The mktemp(), mkstemp() and mkdtemp() functions may also set errno to any value specified by the stat(2) function.

The mkstemp() function may also set errno to any value specified by the open(2) function.

The mkdtemp() function may also set errno to any value specified by the mkdir(2) function.

SEE ALSO
chmod(2), getpid(2), open(2), stat(2)

HISTORY
A mktemp() function appeared in AT&T UNIX.

The mkstemp() function appeared in 4.4BSD.

The mkdtemp() function appeared in NetBSD 1.4.

SECURITY CONSIDERATIONS
The use of mktemp() should generally be avoided, as a hostile process can exploit a race condition in the time between the generation of a temporary filename by mktemp() and the invoker's use of the temporary name. A link-time warning will be issued advising the use of mkstemp() or mkdtemp() instead.