Removing all blank lines, leading and trailing blank spaces

Removing all blank lines, leading and trailing blank spaces :
#sed '/^$/d; s/^[ ]*//g; s/[ ]*$//g' prabhat.txt > kumar.txt

This command will create new file (kumar.txt) on which it removes blank lines, leading and trailing blank spaces.

Remove all empty directories

$ cleanlinks

this is supported on few flavor of Linux (XFree86), you can use this script.

#/bin/bash
DIR="$1"
[ -d $DIR ] && [ $(ls -l $DIR | wc -l) -eq 1 ] && rmdir $DIR || :

$ script.sh dir1

Removing blank line from file

Using sed.
$ sed '/^$/d' withblankline.txt > withoutblankline.txt
Using grep.
$ grep -v '^$' withblankline.txt > withoutblankline.txt

Use following for loop (shell script) to remove all blank lines from all files stored in /home/prabhat/data directory:

#!/bin/sh
files="/home/prabhat/data/*.txt"
for f in $files
do
sed '/^$/d' $i > $i.out
mv $i.out $i
done