registry team mailing list archive

[C de-Avillez <carlos.de.avillez@xxxxxxxxxxxxx>]

Also, meanwhile, here's the info output for coreutils 8.5:

*NOTE* --suffix does not work on current Lucid (or older) coreutils.

File: coreutils.info,  Node: mktemp invocation,  Prev: pathchk
invocation,  Up: File name manipulation

18.4 `mktemp': Create temporary file or directory
=================================================

`mktemp' manages the creation of temporary files and directories.
Synopsis:

     mktemp [OPTION]... [TEMPLATE]

   Safely create a temporary file or directory based on TEMPLATE, and
print its name.  If given, TEMPLATE must include at least three
consecutive `X's in the last component.  If omitted, the template
`tmp.XXXXXXXXXX' is used, and option `--tmpdir' is implied.  The final
run of `X's in the TEMPLATE will be replaced by alpha-numeric
characters; thus, on a case-sensitive file system, and with a TEMPLATE
including a run of N instances of `X', there are `62**N' potential file
names.

   Older scripts used to create temporary files by simply joining the
name of the program with the process id (`$$') as a suffix.  However,
that naming scheme is easily predictable, and suffers from a race
condition where the attacker can create an appropriately named symbolic
link, such that when the script then opens a handle to what it thought
was an unused file, it is instead modifying an existing file.  Using
the same scheme to create a directory is slightly safer, since the
`mkdir' will fail if the target already exists, but it is still
inferior because it allows for denial of service attacks.  Therefore,
modern scripts should use the `mktemp' command to guarantee that the
generated name will be unpredictable, and that knowledge of the
temporary file name implies that the file was created by the current
script and cannot be modified by other users.

   When creating a file, the resulting file has read and write
permissions for the current user, but no permissions for the group or
others; these permissions are reduced if the current umask is more
restrictive.

   Here are some examples (although note that if you repeat them, you
will most likely get different file names):

   * Create a temporary file in the current directory.
          $ mktemp file.XXXX
          file.H47c

   * Create a temporary file with a known suffix.
          $ mktemp --suffix=.txt file-XXXX
          file-H08W.txt
          $ mktemp file-XXXX-XXXX.txt
          file-XXXX-eI9L.txt

   * Create a secure fifo relative to the user's choice of `TMPDIR',
     but falling back to the current directory rather than `/tmp'.
     Note that `mktemp' does not create fifos, but can create a secure
     directory in which the fifo can live.  Exit the shell if the
     directory or fifo could not be created.
          $ dir=$(mktemp -p "${TMPDIR:-.}" -d dir-XXXX) || exit 1
          $ fifo=$dir/fifo
          $ mkfifo "$fifo" || { rmdir "$dir"; exit 1; }

   * Create and use a temporary file if possible, but ignore failure.
     The file will reside in the directory named by `TMPDIR', if
     specified, or else in `/tmp'.
          $ file=$(mktemp -q) && {
          >   # Safe to use $file only within this block.  Use quotes,
          >   # since $TMPDIR, and thus $file, may contain whitespace.
          >   echo ... > "$file"
          >   rm "$file"
          > }

   * Act as a semi-random character generator (it is not fully random,
     since it is impacted by the contents of the current directory).  To
     avoid security holes, do not use the resulting names to create a
     file.
          $ mktemp -u XXX
          Gb9
          $ mktemp -u XXX
          nzC


   The program accepts the following options.  Also see *note Common
options::.

`-d'
`--directory'
     Create a directory rather than a file.  The directory will have
     read, write, and search permissions for the current user, but no
     permissions for the group or others; these permissions are reduced
     if the current umask is more restrictive.

`-q'
`--quiet'
     Suppress diagnostics about failure to create a file or directory.
     The exit status will still reflect whether a file was created.

`-u'
`--dry-run'
     Generate a temporary name that does not name an existing file,
     without changing the file system contents.  Using the output of
     this command to create a new file is inherently unsafe, as there
     is a window of time between generating the name and using it where
     another process can create an object by the same name.

`-p DIR'
`--tmpdir[=DIR]'
     Treat TEMPLATE relative to the directory DIR.  If DIR is not
     specified (only possible with the long option `--tmpdir') or is
     the empty string, use the value of `TMPDIR' if available,
     otherwise use `/tmp'.  If this is specified, TEMPLATE must not be
     absolute.  However, TEMPLATE can still contain slashes, although
     intermediate directories must already exist.

`--suffix=SUFFIX'
     Append SUFFIX to the TEMPLATE.  SUFFIX must not contain slash.  If
     `--suffix' is specified, TEMPLATE must end in `X'; if it is not
     specified, then an appropriate `--suffix' is inferred by finding
     the last `X' in TEMPLATE.  This option exists for use with the
     default TEMPLATE and for the creation of a SUFFIX that starts with
     `X'.

`-t'
     Treat TEMPLATE as a single file relative to the value of `TMPDIR'
     if available, or to the directory specified by `-p', otherwise to
     `/tmp'.  TEMPLATE must not contain slashes.  This option is
     deprecated; the use of `-p' without `-t' offers better defaults
     (by favoring the command line over `TMPDIR') and more flexibility
     (by allowing intermediate directories).


   Exit status:

     0 if the file was created,
     1 otherwise.


** Description changed:

  Binary package hint: coreutils
  
  $ man 1 mktemp
  [...]
  SEE ALSO
-        mkstemp(3), mkdtemp(3), mktemp(3)
+        mkstemp(3), mkdtemp(3), mktemp(3)
  
-        The full documentation for mktemp is maintained as a Texinfo manual.  If the info and mktemp programs
-        are properly installed at your site, the command
+        The full documentation for mktemp is maintained as a Texinfo manual.  If the info and mktemp programs
+        are properly installed at your site, the command
  
-               info coreutils 'mktemp invocation'
+               info coreutils 'mktemp invocation'
  
-        should give you access to the complete manual.
+        should give you access to the complete manual.
  
  $ info coreutils 'mktemp invocation'
  [...]
  No menu item `mktemp invocation' in node `(coreutils.info.gz)Top'.
  
  And actually - there's does not seem to be any such information anywhere
  in the info pages, as far as I could (not) find.
+ 
+ WORKAROUND: see comment #3 for the 'info' output for coreutils. Also,
+ please heed the *NOTE* there.

-- 
mktemp has no 'info' documentation
https://bugs.launchpad.net/bugs/589404
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