Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
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Example 12−24. stripping comments from C program files
#!/bin/bash
# strip−comment.sh: Strips out the comments (/* COMMENT */) in a C program.
E_NOARGS=65
E_ARGERROR=66
E_WRONG_FILE_TYPE=67
if [ $# −eq "$E_NOARGS" ]
then
echo "Usage: `basename $0` C−program−file" >&2 # Error message to stderr.
exit $E_ARGERROR
fi
# Test for correct file type.
type=`eval file $1 | awk '{ print $2, $3, $4, $5 }'`
# "file $1" echoes file type...
# then awk removes the first field of this, the filename...
# then the result is fed into the variable "type".
correct_type="ASCII C program text"
if [ "$type" != "$correct_type" ]
then
echo
echo "This script works on C program files only."
echo
exit $E_WRONG_FILE_TYPE
fi
# Rather cryptic sed script:
#−−−−−−−−
sed '
/^\/\*/d
/.*\/\*/d
' $1
#−−−−−−−−
# Easy to understand if you take several hours to learn sed fundamentals.
# Need to add one more line to the sed script to deal with
#+ case where line of code has a comment following it on same line.
# This is left as a non−trivial exercise.
# Also, the above code deletes lines with a "*/" or "/*",
# not a desirable result.
exit 0
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
# Code below this line will not execute because of 'exit 0' above.
Chapter 12. External Filters, Programs and Commands 180