Exercise: Shells Scripts

1. Reading Scripts:
   What does the following Unix shell script
   (it runs in for the bash shell) do ?
   Do not try it before understanding what it does! #!/bin/sh N=`basename $0` if [ "$1" = "-v" ] ; then VERBOSE="-v" shift fi if [ "$3" = "" -o "$1" = "-h" -o "$1" = "--help" ] ; then echo "$N: Usage" echo " $N [-h|--help] [-v] <regexp-search> \ <regexp-replace> <glob-file>" echo exit 0 fi S="$1" ; shift ; R="$1" ; shift T=$$replc if echo "$1" | grep -q / ; then for i in "$@" ; do SEARCH=`echo "$S" | sed 's,/,\\\\/,g'` REPLACE=`echo "$R" | sed 's,/,\\\\/,g'` cat $i | sed "s/$SEARCH/$REPLACE/g" > $T D="$?" if [ "$D" = "0" ] ; then if diff -q $T $i >/dev/null ; then : else if [ "$VERBOSE" = "-v" ] ; then echo $i fi cat $T > $i fi rm -f $T fi done else find . -type f -name "$1" | xargs $0 $VERBOSE "$S" "$R" fi
2. Writhing Scripts:
   Write a script that replaces all "*.html" file names
   with "*.html.old" in the current directory.