mkstemp(3) - NetBSD Manual Pages

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MKTEMP(3)                 NetBSD Programmer's Manual                 MKTEMP(3)


NAME

     mktemp, mkstemp - make temporary file name (unique)


SYNOPSIS

     #include <unistd.h>

     char *
     mktemp(char *template);

     int
     mkstemp(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 suit-
     able 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.


RETURN VALUES

     The mktemp() function returns 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() and mkstemp() functions may set errno to one of the follow-
     ing values:

     [ENOTDIR]     The pathname portion of the template is not an existing di-
                   rectory.

     The mktemp() and mkstemp() 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.


SEE ALSO

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


HISTORY

     A mktemp() function appeared in Version 7 AT&T UNIX.


BUGS

     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 tempo-
     rary filename by mktemp() and the invoker's use of the temporary name.  A
     link-time warning will be issued to advise the use of mkstemp() instead.

4.4BSD                          March 24, 1997                               1