mkdtemp(3p) — Linux manual page

PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

MKDTEMP(3P)             POSIX Programmer's Manual            MKDTEMP(3P)

PROLOG         top

       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         top

       mkdtemp, mkstemp — create a unique directory or file

SYNOPSIS         top

       #include <stdlib.h>

       char *mkdtemp(char *template);
       int mkstemp(char *template);

DESCRIPTION         top

       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         top

       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         top

       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(3p).

       The following sections are informative.

EXAMPLES         top

   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         top

       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         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       getpid(3p), mkdir(3p), open(3p), tmpfile(3p), tmpnam(3p)

       The Base Definitions volume of POSIX.1‐2017, stdlib.h(0p)

COPYRIGHT         top

       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 .

IEEE/The Open Group               2017                       MKDTEMP(3P)

Pages that refer to this page: stdlib.h(0p)getpid(3p)mkdir(3p)mkstemp(3p)open(3p)tempnam(3p)tmpfile(3p)tmpnam(3p)