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NAME
mkstemp - make a unique filename
SYNOPSIS
#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.
The following sections are informative.
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>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers,
Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The
original Standard can be obtained online at http://www.opengroup.org/unix/online.html .