man3/mkstemp.3

   1 .\" Copyright 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 18:48:48 1993 by Rik Faith (faith@cs.unc.edu)
  28 .\" Modified 980310, aeb
  29 .\" Modified 990328, aeb
  30 .\"
  31 .TH MKSTEMP 3  2001-12-23 "GNU" "Linux Programmer's Manual"
  32 .SH NAME
  33 mkstemp \- create a unique temporary file
  34 .SH SYNOPSIS
  35 .nf
  36 .B #include <stdlib.h>
  37 .sp
  38 .BI "int mkstemp(char *" template );
  39 .fi
  40 .SH DESCRIPTION
  41 The
  42 .BR mkstemp ()
  43 function generates a unique temporary filename
  44 from \fItemplate\fP.
  45 The last six characters of \fItemplate\fP must
  46 be XXXXXX and these are replaced with a string that makes the
  47 filename unique.
  48 The file is then created with mode read/write and
  49 permissions 0666 (glibc 2.0.6 and earlier), 0600 (glibc 2.0.7 and later).
  50 Since it will be modified,
  51 .I template
  52 must not be a string constant, but should be declared as a character array.
  53 The file is opened with the
  54 .BR open (2)
  55 .B O_EXCL
  56 flag, guaranteeing that when
  57 .BR mkstemp ()
  58 returns successfully we are the only user.
  59 .SH "RETURN VALUE"
  60 On success, the
  61 .BR mkstemp ()
  62 function returns the file descriptor
  63 of the temporary file.
  64 On error, \-1 is returned, and
  65 .I errno
  66 is set appropriately.
  67 .SH ERRORS
  68 .TP
  69 .B EEXIST
  70 Could not create a unique temporary filename.
  71 Now the contents of \fItemplate\fP are undefined.
  72 .TP
  73 .B EINVAL
  74 The last six characters of \fItemplate\fP were not XXXXXX.
  75 Now \fItemplate\fP is unchanged.
  76 .SH "CONFORMING TO"
  77 4.3BSD, POSIX.1-2001
  78 .SH NOTES
  79 The old behavior (creating a file with mode 0666) may be
  80 a security risk, especially since other Unix flavors use 0600,
  81 and somebody might overlook this detail when porting programs.
  82
  83 More generally, the POSIX specification does not say anything
  84 about file modes, so the application should make sure its umask
  85 is set appropriately before calling
  86 .BR mkstemp ().
  87
  88 The prototype is in
  89 .I <unistd.h>
  90 for libc4, libc5, glibc1; glibc2 follows POSIX.1 and has the prototype in
  91 .IR <stdlib.h> .
  92 .SH "SEE ALSO"
  93 .BR mkdtemp (3),
  94 .BR mktemp (3),
  95 .BR tempnam (3),
  96 .BR tmpfile (3),
  97 .BR tmpnam (3)