view bin/example/self-writing.sh @ 383:8d1ad56761b0

this still, somehow, eludes my tired brain
author Jeff Hammel <jhammel@mozilla.com>
date Fri, 26 Jul 2013 05:56:18 -0700
parents aae9b0776e60
children
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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`
mode=`stat --format '%a' ${path}`
tmp=`tempfile --mode ${mode}`
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 Sat Jun  8 08:52:35 PDT 2013"
echo "Now: ${datestamp}"

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