MKSTEMP - A wrapper of mktemp(1) to behave as a equivalent of mkstemp(1)

mkstemp

#! /bin/sh

######################################################################
#
# MKSTEMP : A wrapper of mktemp(1) to behave as a equivalent of mkstemp(1)
#
# Written by Rich Mikan (richmikan[at]richlab.org) at 2013/11/09
#
# Usage  : mkstemp [mktemp(1)options] <template>
#
# * <template> is necessary. And only 1.
# * "mktemp(1) options" depend on mktemp(1) on the host
#
######################################################################

# --- definition: print the usage and exit ---------------------------
print_usage_and_exit () {
  cat <<-__USAGE 1>&2
	Usage   : ${0##*/} [mktemp(1)options] <template>
	          "mktemp(1) options" depend on mktemp(1) on the host.
	Version : Sat Nov 09 23:23:10 JST 2013
__USAGE
  exit 1
}

# --- definition: characters for substituting the "XXX..." string ----
chrs='0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz_'
xchrslen=$(echo "obase=16;${#chrs}" | bc)

# --- parse the arguments --------------------------------------------
[ $# -ge 1 ] || print_usage_and_exit
i=1
options=''
for arg in "$@"; do
  if [ $i -lt $# ]; then
    options="$options $arg"
  else
    template=$arg
  fi
  i=$((i+1))
done

# --- separate filepath ----------------------------------------------
s=${template%/*}
if [ "_$s" != "_$template" ]; then
  path=$s
else
  path='.'
fi

# --- count the number of the tail "X" characters --------------------
template_without_x=$(echo "_$template" | sed '1s/^_//' | sed 's/X*$//')
variable_len=$((${#template}-${#template_without_x}))

# --- validate the path ----------------------------------------------
[ -d "$path" ] || { echo "${0##*/}: No such directory" 1>&2; exit 1; }

# --- make a temporary file (for non "X" terminated string) ----------
if [ $variable_len -eq 0 ]; then
  exec mktemp $options "$template_without_x"
fi

# --- make a temporary file (for "X" terminated string) --------------
bytes=$(awk 'BEGIN{print int('$variable_len'*log('${#chrs}')/log(256))+1}')
i=100  # <- time to retry
while [ $i -gt 0 ]; do
  i=$((i-1))
  rndstr=$(cat /dev/urandom                                         |
           head -c $bytes                                           |
           od -v -An -tx1                                           |
           tr -Cd '0-9a-fA-F'                                       |
           tr 'a-f' 'A-F'                                           |
           awk '{print "ibase=16; obase='$xchrslen'; " $1}'         |
           bc                                                       |
           tr -d '\\\n'                                             |
           awk '{ORS="";                                            #
                 split("'"$chrs"'",chrs,""); split($0,digits);      #
                 for (pos in digits) {print chrs[digits[pos]+1];}}' |
           head -c $variable_len                                    )
  if [ $i -gt 0 ]; then
    made_file=$(mktemp $options "$template_without_x$rndstr" 2>/dev/null)
    [ $? -eq 0        ] || continue
    [ -n "$made_file" ] || continue
    break
  else
    exec mktemp $options "$template_without_x$rndstr"
  fi
done
echo "$made_file"

# --- finish ---------------------------------------------------------
exit 0

2013/11/09: first release