1.\" Copyright (c) 1989, 1991 The Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" %sccs.include.redist.man% 5.\" 6.\" @(#)mktemp.3 6.10 (Berkeley) 04/19/91 7.\" 8.Dd 9.Dt MKTEMP 3 10.Os 11.Sh NAME 12.Nm mktemp 13.Nd make temporary file name (unique) 14.Sh SYNOPSIS 15.Fd #include <unistd.h> 16.Ft char * 17.Fn mktemp "char *template" 18.Ft int 19.Fn mkstemp "char *template" 20.Sh DESCRIPTION 21The 22.Fn mktemp 23function 24takes the given file name template and overwrites a portion of it 25to create a file name. 26This file name is unique and suitable for use 27by the application. 28The template may be any file name with some number of 29.Ql X Ns s 30appended 31to it, for example 32.Pa /tmp/temp.XXXX . 33The trailing 34.Ql X Ns s 35are replaced with the current process number and/or a 36unique letter combination. 37The number of unique file names 38.Fn mktemp 39can return depends on the number of 40.Ql X Ns s 41provided; six 42.Ql X Ns s 43will 44result in 45.Fn mktemp 46testing roughly 26 ** 6 combinations. 47.Pp 48The 49.Fn mkstemp 50function 51makes the same replacement to the template and creates the template file, 52mode 0600, returning a file descriptor opened for reading and writing. 53This avoids the race between testing for a file's existence and opening it 54for use. 55.Sh RETURN VALUES 56The 57.Fn mktemp 58function 59returns a pointer to the template on success and 60.Dv NULL 61on failure. 62The 63.Fn mkstemp 64function 65returns \-1 if no suitable file could be created. 66If either call fails an error code is placed in the global variable 67.Va errno . 68.Sh ERRORS 69The 70.Fn mktemp 71and 72.Fn mkstemp 73functions 74may set 75.Va errno 76to one of the following values: 77.Bl -tag -width [ENOTDIR] 78.It Bq Er ENOTDIR 79The pathname portion of the template is not an existing directory. 80.El 81.Pp 82The 83.Fn mktemp 84and 85.Fn mkstemp 86functions 87may also set 88.Va errno 89to any value specified by the 90.Xr stat 2 91function. 92.Pp 93The 94.Fn mkstemp 95function 96may also set 97.Va errno 98to any value specified by the 99.Xr open 2 100function. 101.Sh SEE ALSO 102.Xr chmod 2 , 103.Xr getpid 2 , 104.Xr open 2 , 105.Xr stat 2 106.Sh HISTORY 107A 108.Nm mktemp 109function appeared in 110.At v7 . 111