Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
# Inspired by a script of John Dubois,
# which was translated into into Bash by Chet Ramey,
# and considerably simplified by Mendel Cooper, author of this document.
for filename in *
# Traverse all files in directory.
do
fname=`basename $filename`
n=`echo $fname | tr A−Z a−z` # Change name to lowercase.
if [ "$fname" != "$n" ] # Rename only files not already lowercase.
then
mv $fname $n
fi
done
exit 0
# Code below this line will not execute because of "exit".
#−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−#
# To run it, delete script above line.
# The above script will not work on filenames containing blanks or newlines.
# Stephane Chazelas therefore suggests the following alternative:
for filename in * # Not necessary to use basename,
# since "*" won't return any file containing "/".
do n=`echo "$filename/" | tr '[:upper:]' '[:lower:]'`
# POSIX char set notation.
# Slash added so that trailing newlines are not
# removed by command substitution.
# Variable substitution:
n=${n%/}
# Removes trailing slash, added above, from filename.
[[ $filename == $n ]] || mv "$filename" "$n"
# Checks if filename already lowercase.
done
exit 0
Example 12−16. du: DOS to UNIX text file conversion.
#!/bin/bash
# du.sh: DOS to UNIX text file converter.
E_WRONGARGS=65
if [ −z "$1" ]
then
echo "Usage: `basename $0` filename−to−convert"
exit $E_WRONGARGS
fi
NEWFILENAME=$1.unx
CR='\015' # Carriage return.
# Lines in a DOS text file end in a CR−LF.
tr −d $CR < $1 > $NEWFILENAME
Chapter 12. External Filters, Programs and Commands 172