mkstemp(), mkstemps()

Make a unique temporary filename and open the file

Synopsis:

#include <stdlib.h>

int mkstemp( char* template );

int mkstemps( char *template,
              int slen );

Arguments:

template: A template for the filename that you want to use. For mkstemp(), this template can be any file name with at least six X characters appended to it (for example, /tmp/temp.XXXXXX); for mkstemps(), it also includes a suffix (e.g., /tmp/temp.XXXXXXsuffix).
slen: (mkstemps() only) The length of the suffix included in the template.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The mkstemp() and mkstemps() functions take the given file name template and overwrite a portion of it to create a filename.

The generated file name is unique and suitable for use by the application. The Xs are replaced with the current process number and/or a unique letter combination. The number of unique file names that these functions can return depends on the number of Xs provided; the functions try at least 2³¹ combinations before giving up.

The mkstemp() and mkstemps() functions (unlike mktemp()) create the template file, mode 0600 (i.e., read-write for the owner), 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.

Returns:

The file descriptor of the temporary file, or -1 if no suitable file could be created (errno is set).

Errors:

EINVAL: The template doesn't include at least six X wildcard characters, or (for mkstemps()) the length of the template is less than slen.
EEXIST: All the names tried already exist. Consider adding more wildcard characters to the template.

This function may also set errno to any value specified by open().

Classification:

mkstemp() is POSIX 1003.1; mkstemps() is OpenBSD

Safety:
Cancellation point	Yes
Interrupt handler	No
Signal handler	Yes
Thread	Yes