MKDTEMP
Section: POSIX Programmer's Manual (3P)
Updated: 2017
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PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
NAME
mkdtemp, mkstemp
--- create a unique directory or file
SYNOPSIS
#include <stdlib.h>
char *mkdtemp(char *template);
int mkstemp(char *template);
DESCRIPTION
The
mkdtemp()
function shall create a directory with a unique name derived from
template.
The application shall ensure that the string provided in
template
is a pathname ending with at least six trailing
'X'
characters. The
mkdtemp()
function shall modify the contents of
template
by replacing six or more
'X'
characters at the end of the pathname with the same number of
characters from the portable filename character set. The characters
shall be chosen such that the resulting pathname does not duplicate
the name of an existing file at the time of the call to
mkdtemp().
The
mkdtemp()
function shall use the resulting pathname to create the new directory
as if by a call to:
-
mkdir(pathname, S_IRWXU)
The
mkstemp()
function shall create a regular file with a unique name derived from
template
and return a file descriptor for the file open for reading and
writing. The application shall ensure that the string provided in
template
is a pathname ending with at least six trailing
'X'
characters. The
mkstemp()
function shall modify the contents of
template
by replacing six or more
'X'
characters at the end of the pathname with the same number of
characters from the portable filename character set. The characters
shall be chosen such that the resulting pathname does not duplicate
the name of an existing file at the time of the call to
mkstemp().
The
mkstemp()
function shall use the resulting pathname to create the file, and
obtain a file descriptor for it, as if by a call to:
-
open(pathname, O_RDWR|O_CREAT|O_EXCL, S_IRUSR|S_IWUSR)
By behaving as if the O_EXCL flag for
open()
is set, the function prevents any possible race condition between
testing whether the file exists and opening it for use.
RETURN VALUE
Upon successful completion, the
mkdtemp()
function shall return the value of
template.
Otherwise, it shall return a null pointer and shall set
errno
to indicate the error.
Upon successful completion, the
mkstemp()
function shall return an open file descriptor. Otherwise, it shall
return -1 and shall set
errno
to indicate the error.
ERRORS
The
mkdtemp()
function shall fail if:
- EACCES
-
Search permission is denied on a component of the path prefix, or write
permission is denied on the parent directory of the directory to be
created.
- EINVAL
-
The string pointed to by
template
does not end in
"XXXXXX".
- ELOOP
-
A loop exists in symbolic links encountered during resolution of the
path of the directory to be created.
- EMLINK
-
The link count of the parent directory would exceed
{LINK_MAX}.
- ENAMETOOLONG
-
The length of a component of a pathname is longer than
{NAME_MAX}.
- ENOENT
-
A component of the path prefix specified by the
template
argument does not name an existing directory.
- ENOSPC
-
The file system does not contain enough space to hold the contents of
the new directory or to extend the parent directory of the new
directory.
- ENOTDIR
-
A component of the path prefix names an existing file that is neither
a directory nor a symbolic link to a directory.
- EROFS
-
The parent directory resides on a read-only file system.
The
mkdtemp()
function may fail if:
- ELOOP
-
More than
{SYMLOOP_MAX}
symbolic links were encountered during resolution of the path of the
directory to be created.
- ENAMETOOLONG
-
The length of a pathname exceeds
{PATH_MAX},
or pathname resolution of a symbolic link produced an intermediate
result with a length that exceeds
{PATH_MAX}.
The error conditions for the
mkstemp()
function are defined in
open().
The following sections are informative.
EXAMPLES
Generating a Pathname
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.
Portable applications should pass exactly six trailing
'X's
in the template and no more; implementations may treat any additional
trailing
'X's
as either a fixed or replaceable part of the template. To be sure of
only passing six, a fixed string of at least one non-'X'
character should precede the six
'X's.
Since
'X'
is in the portable filename character set, some of the replacement
characters can be
'X's,
leaving part (or even all) of the template effectively unchanged.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
getpid(),
mkdir(),
open(),
tmpfile(),
tmpnam()
The Base Definitions volume of POSIX.1-2017,
<stdlib.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 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 .
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
Index
- PROLOG
-
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- EXAMPLES
-
- Generating a Pathname
-
- APPLICATION USAGE
-
- RATIONALE
-
- FUTURE DIRECTIONS
-
- SEE ALSO
-
- COPYRIGHT
-
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