Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
#!/bin/bash
# wstrings.sh: "word−strings" (enhanced "strings" command)
#
# This script filters the output of "strings" by checking it
#+ against a standard word list file.
# This effectively eliminates all the gibberish and noise,
#+ and outputs only recognized words.
# =================================================================
# Standard Check for Script Argument(s)
ARGS=1
E_BADARGS=65
E_NOFILE=66
if [ $# −ne $ARGS ]
then
echo "Usage: `basename $0` filename"
exit $E_BADARGS
fi
if [ −f "$1" ]
# Check if file exists.
then
file_name=$1
else
echo "File \"$1\" does not exist."
exit $E_NOFILE
fi
# =================================================================
MINSTRLEN=3
# Minimum string length.
WORDFILE=/usr/share/dict/linux.words # Dictionary file.
# May specify a different
#+ word list file
#+ of format 1 word per line.
wlist=`strings "$1" | tr A−Z a−z | tr '[:space:]' Z | \
tr −cs '[:alpha:]' Z | tr −s '\173−\377' Z | tr Z ' '`
# Translate output of 'strings' command with multiple passes of 'tr'.
# "tr A−Z a−z" converts to lowercase.
# "tr '[:space:]'" converts whitespace characters to Z's.
# "tr −cs '[:alpha:]' Z" converts non−alphabetic characters to Z's,
#+ and squeezes multiple consecutive Z's.
# "tr −s '\173−\377' Z" converts all characters past 'z' to Z's
#+ and squeezes multiple consecutive Z's,
#+ which gets rid of all the weird characters that the previous
#+ translation failed to deal with.
# Finally, "tr Z ' '" converts all those Z's to whitespace,
#+ which will be seen as word separators in the loop below.
# Note the technique of feeding the output of 'tr' back to itself,
#+ but with different arguments and/or options on each pass.
for word in $wlist
do
# Important:
# $wlist must not be quoted here.
# "$wlist" does not work.
# Why?
Chapter 12. External Filters, Programs and Commands 183