annotate bin/example/self-writing.sh @ 540:8c9cd7472d28

.bashrc
author Jeff Hammel <jhammel@mozilla.com>
date Fri, 27 Sep 2013 11:50:54 -0700
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1 #!/bin/bash
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2
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3 # illustrate self-writing script (example)
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4 # This one does something hard and replaces dynamic data with sed.
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5 # Other solutions (magic markers, etc) are possible
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6
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7 path=`readlink -f $0`
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8 mode=`stat --format '%a' ${path}`
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9 tmp=`tempfile --mode ${mode}`
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10 datestamp=`date`
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11 nonce="This script last generated at "
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12
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13 # sanity check
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14 if [[ ! -w "${path}" ]]
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15 then
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16 echo "You don't have write permission for script ${path}"
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17 exit 1
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18 fi
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20 # avoiding -i for safety
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21 sed 's/\(echo \"'"${nonce}"'\).*\"/\1'"${datestamp}"'\"/' ${path} > ${tmp}
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22 if [[ ! -e "${tmp}" ]]
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23 then
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24 echo "Temporary file creation not successful"
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25 exit 1
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26 fi
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28 # echo last and current generation times for example
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29 echo "This script last generated at Sat Jun 8 08:52:35 PDT 2013"
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30 echo "Now: ${datestamp}"
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31
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32 # move tmpfile -> script location via exec
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33 exec mv ${tmp} ${path}