man3/mktemp.3

   1 .\" Copyright (C) 1993 David Metcalfe (david@prism.demon.co.uk)
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  23 .\" References consulted:
  24 .\"     Linux libc source code
  25 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  26 .\"     386BSD man pages
  27 .\" Modified Sat Jul 24 18:48:06 1993 by Rik Faith (faith@cs.unc.edu)
  28 .\" Modified Fri Jun 23 01:26:34 1995 by Andries Brouwer (aeb@cwi.nl)
  29 .\" (prompted by Scott Burkett <scottb@IntNet.net>)
  30 .\" Modified Sun Mar 28 23:44:38 1999 by Andries Brouwer (aeb@cwi.nl)
  31 .\"
  32 .TH MKTEMP 3  1993-04-03 "GNU" "Linux Programmer's Manual"
  33 .SH NAME
  34 mktemp \- make a unique temporary filename
  35 .SH SYNOPSIS
  36 .nf
  37 .B #include <stdlib.h>
  38 .sp
  39 .BI "char *mktemp(char *" template );
  40 .fi
  41 .SH DESCRIPTION
  42 The \fBmktemp\fP() function generates a unique temporary filename
  43 from \fItemplate\fP.  The last six characters of \fItemplate\fP must
  44 be XXXXXX and these are replaced with a string that makes the
  45 filename unique.
  46 Since it will be modified,
  47 .I template
  48 must not be a string constant, but should be declared as a character array.
  49 .SH "RETURN VALUE"
  50 The \fBmktemp\fP() function returns NULL on error (\fItemplate\fP did not
  51 end in XXXXXX) and \fItemplate\fP otherwise.
  52 If the call was successful, the last six bytes of \fItemplate\fP will
  53 have been modified in such a way that the resulting name is unique
  54 (does not exist already).
  55 If the call was unsuccessful, \fItemplate\fP
  56 is made an empty string.
  57 .SH ERRORS
  58 .TP
  59 .B EINVAL
  60 The last six characters of \fItemplate\fP were not XXXXXX.
  61 .SH "CONFORMING TO"
  62 4.3BSD, POSIX.1-2001.
  63 .SH NOTE
  64 The prototype is in
  65 .I <unistd.h>
  66 for libc4, libc5, glibc1; glibc2 follows the Single Unix Specification
  67 and has the prototype in
  68 .IR <stdlib.h> .
  69 .SH BUGS
  70 Never use \fBmktemp\fP().
  71 Some implementations follow 4.3BSD
  72 and replace XXXXXX by the current process ID and a single letter,
  73 so that at most 26 different names can be returned.
  74 Since on the one hand the names are easy to guess, and on the other
  75 hand there is a race between testing whether the name exists and
  76 opening the file, every use of \fBmktemp\fP() is a security risk.
  77 The race is avoided by
  78 .BR mkstemp (3).
  79 .SH "SEE ALSO"
  80 .BR mkstemp (3),
  81 .BR tempnam (3),
  82 .BR tmpfile (3),
  83 .BR tmpnam (3)