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.\"     @(#)mktemp.3	8.1 (Berkeley) 6/4/93
.\"
.Dd July 28, 1998
.Dt MKTEMP 3
.Os
.Sh NAME
.Nm mktemp ,
.Nm mkstemp ,
.Nm mkdtemp
.Nd make unique temporary file or directory name
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.Fd #include <stdlib.h>
.Ft char *
.Fn mktemp "char *template"
.Ft int
.Fn mkstemp "char *template"
.Ft char *
.Fn mkdtemp "char *template"
.Sh DESCRIPTION
The
.Fn 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 suitable for use
by the application.
The template may be any file name with some number of
.Ql X Ns s
appended
to it, for example
.Pa /tmp/temp.XXXX .
The trailing
.Ql X Ns s
are replaced with the current process number and/or a
unique letter combination.
The number of unique file names
.Fn mktemp
can return depends on the number of
.Ql X Ns s
provided; six
.Ql X Ns s
will
result in
.Fn mktemp
testing roughly 26 ** 6 combinations.
.Pp
The
.Fn 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.
.Pp
The
.Fn mkdtemp
function
is similar to
.Fn mkstemp ,
but it creates a mode 0700 directory instead and returns the path.
.Pp
Please note that the permissions of the file or directory being created are
subject to the restrictions imposed by the
.Xr umask 2
system call. It may thus happen that the created file is unreadable and/or
unwritable.
.Sh RETURN VALUES
The
.Fn mktemp
and
.Fn mkdtemp
functions
return a pointer to the template on success and
.Dv NULL
on failure.
The
.Fn mkstemp
function
returns \-1 if no suitable file could be created.
If either call fails an error code is placed in the global variable
.Va errno .
.Sh ERRORS
The
.Fn mktemp ,
.Fn mkstemp
and
.Fn mkdtemp
functions
may set
.Va errno
to one of the following values:
.Bl -tag -width Er
.It Bq Er ENOTDIR
The pathname portion of the template is not an existing directory.
.El
.Pp
The
.Fn mktemp ,
.Fn mkstemp
and
.Fn mkdtemp
functions
may also set
.Va errno
to any value specified by the
.Xr stat 2
function.
.Pp
The
.Fn mkstemp
function
may also set
.Va errno
to any value specified by the
.Xr open 2
function.
.Pp
The
.Fn mkdtemp
function
may also set
.Va errno
to any value specified by the
.Xr mkdir 2
function.
.Sh SEE ALSO
.Xr chmod 2 ,
.Xr getpid 2 ,
.Xr open 2 ,
.Xr stat 2 ,
.Xr umask 2
.Sh HISTORY
A
.Fn mktemp
function appeared in
.At v7 .
.Pp
The
.Fn mkstemp
function appeared in
.Bx 4.4 .
.Pp
The
.Fn mkdtemp
function appeared in
.Nx 1.4 .
.Sh SECURITY CONSIDERATIONS
The use of
.Fn mktemp
should generally be avoided, as a hostile process can exploit a race
condition in the time between the generation of a temporary filename by
.Fn mktemp
and the invoker's use of the temporary name.
A link-time warning will be issued advising the use of
.Fn mkstemp
or
.Fn mkdtemp
instead.