view bin/example/self-writing.sh @ 326:dbb6ef0c9a26

ya gotta update your nonce
author Jeff Hammel <jhammel@mozilla.com>
date Sat, 08 Jun 2013 08:48:26 -0700
parents bc2d0d504270
children 59f402cd9d98
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#!/bin/bash

# illustrate self-writing script (example)
# This one does something hard and replaces dynamic data with sed.
# Other solutions (magic markers, etc) are possible

path=`readlink -f $0`
tmp=`tempfile --mode 0755`
datestamp=`date`
nonce="This script last generated at "

# sanity check
if [[ ! -w "${path}" ]]
then
    echo "You don't have write permission for script ${path}"
    exit 1
fi

# avoiding -i for safety
sed 's/\(echo \"'"${nonce}"'\).*\"/\1'"${datestamp}"'\"/' ${path} > ${tmp}
if [[ ! -e "${tmp}" ]]
then
    echo "Temporary file creation not successful"
    exit 1
fi

# echo last and current generation times for example
echo "This script last generated at (None)"
echo "Now: ${datestamp}"

# move tmpfile -> script location via exec
exec mv ${tmp} ${path}