examples/scripts.noah/mktmp.bash

   1 # mktmp.bash
   2 # Author: Noah Friedman <friedman@prep.ai.mit.edu>
   3 # Created: 1993-02-03
   4 # Last modified: 1993-02-03
   5 # Public domain
   6
   7 # Conversion to bash v2 syntax done by Chet Ramey
   8
   9 # Commentary:
  10 # Code:
  11
  12 #:docstring mktmp:
  13 # Usage: mktmp [template] {createp}
  14 #
  15 # Generate a unique filename from TEMPLATE by appending a random number to
  16 # the end.
  17 #
  18 # If optional 2nd arg CREATEP is non-null, file will be created atomically
  19 # before returning.  This is to avoid the race condition that in between
  20 # the time that the temporary name is returned and the caller uses it,
  21 # someone else creates the file.
  22 #:end docstring:
  23
  24 ###;;;autoload
  25 function mktmp ()
  26 {
  27     local template="$1"
  28     local tmpfile="${template}${RANDOM}"
  29     local createp="$2"
  30     local noclobber_status
  31
  32     case "$-" in
  33     *C*)        noclobber_status=set;;
  34     esac
  35
  36     if [ "${createp:+set}" = "set" ]; then
  37        # Version which creates file atomically through noclobber test.
  38        set -o noclobber
  39        (> "${tmpfile}") 2> /dev/null
  40        while [ $? -ne 0 ] ; do
  41           # Detect whether file really exists or creation lost because of
  42           # some other permissions problem.  If the latter, we don't want
  43           # to loop forever.
  44           if [ ! -e "${tmpfile}" ]; then
  45              # Trying to create file again creates stderr message.
  46              echo -n "mktmp: " 1>&2
  47              > "${tmpfile}"
  48              return 1
  49           fi
  50           tmpfile="${template}${RANDOM}"
  51           (> "${tmpfile}") 2> /dev/null
  52        done
  53        test "${noclobber_status}" != "set" && set +o noclobber
  54     else
  55        # Doesn't create file, so it introduces race condition for caller.
  56        while [ -e "${tmpfile}" ]; do
  57           tmpfile="${template}${RANDOM}"
  58        done
  59     fi
  60
  61     echo "${tmpfile}"
  62 }
  63
  64 provide mktmp
  65
  66 # mktmp.bash ends here