Shell Programming and Scripting

$ ls
monkey.txt
banana.csv
tree.txt
$ myscript monkey.txt tree.txt
All extensions ARE alike.
$ myscript *txt
All extensions ARE alike.
$ myscript monkey.txt banana.csv
All extensions are NOT alike.
$ myscript *
All extensions are NOT alike.

if [ $# -gt 1 ]; then
        for (( i=1; i<$#; i++ )); do
                if [ "$i##*.}" != "$i+1##*.}" ]; then
                        echo "All extensions are NOT alike."
                        exit 1
                fi
        done
fi
echo "All extensions ARE alike."

if [ $# -gt 1 ]; then
        for (( i=1; i<$#; i++ )); do
                j=`expr $i + 1`
                if eval [ '${'${i}'##*.}' != '${'${j}'##*.}' ]; then
                        echo "All extensions are NOT alike."
                        exit 1
                fi
        done
fi
echo "All extensions ARE alike."

if [ $# -gt 1 ]; then
        for (( i=1; i<$#; i++ )); do
                if [ "$(eval echo '${'$i'}' | sed 's/^[^\.]*//')" != "$(eval echo '${'$((i+1))'}' | sed 's/^[^\.]*//')" ]; then
                        echo "All extensions are NOT alike."
                        exit 1
                fi
        done
fi
echo "All extensions ARE alike."

#!bin/ksh or bash or ...
[ "$#" -lt 1 ] && echo "need args" >&2 && exit 1

IFS="."
token=($1)
cnt=${#token[*]}
((last=cnt-1))
shift
while [ $# -gt 0 ]
do
        mytoken=($1)
        mycnt=${#mytoken[*]}
        ((mylast=mycnt-1))
        ((cnt==1 && mycnt != 1)) && echo "All extensions are NOT alike." && exit 2
        [ "${mytoken[$mylast]}" != "${token[$last]}" ] && echo "All extensions are NOT alike." && exit 3
        shift
done

echo "All extensions ARE alike"

#!/bin/sh
for i in `echo $*`
do
echo $i |awk -F. '{print $2}'|sort >>text
done
cat text|uniq -c |awk 'END{ {if(NR > 1)print "diff"
else print "same"}}'
rm -f text

if [ `for file in $@; do
                echo ${file} | sed 's/^[^\.]*//'
        done | uniq -c | wc -l` -gt 1 ]; then
                echo "All extensions are NOT alike."
                exit 1
        else
                echo "All extensions ARE alike."
fi

if [ `for file in $@; do
                echo ${file##*.}
        done | uniq -c | wc -l` -gt 1 ]; then
                echo "All extensions are NOT alike."
                exit 1
        else
                echo "All extensions ARE alike."
fi

#!/bin/sh

set_e() {
    e=${1#*.}
    [ "$e" = "$1" ] && e=''
}

set_e "$1"
ext=$e

for f; do
    set_e "$f"
    [ "$ext" = "$e" ] || exit 1
done
exit 0