• Difficulty: Easy
• Application: KStars

You may already have played with KStars, but how about creating a KStars backdrop image that’s updated every time you start up?

KStars can be run with the –dump switch, which dumps out an image from your startup settings, but doesn’t load the GUI at all. You can create a script to run this and generate a desktop image, which will change every day (or you can just use this method to generate images).

Run KStars like this:

kstars --dump --width 1024 --height 768 --filename = ~/kstarsback.png

You can add this to a script in your ~/.kde/Autostart folder to be run at startup. Find the file in Konqueror, drag it to the desktop and select ‘Set as wallpaper’ to use it as a randomly generated backdrop.

Open an SVG directly

• Difficulty: Easy
• Application: Inkscape

You can run Inkscape from a shell and immediately edit a graphic directly from a URL. Just type:

inkscape http://www.somehost.com/graphic.svg

Remember to save it as something else though!

Editing without an editor

• Difficulty: Intermediate
• Application: Various

Very long files are often hard to manipulate with a text editor. If you need to do it regularly, chances are you’ll find it much faster to use some handy command-line tools instead, like in the following examples.

To print columns eg 1 and 3 from a file file1 into file2, we can use awk:

awk '{print $1, $3}' file1 > file2

To output only characters from column 8 to column 15 of file1, we can use cut:

cut -c 8-15 file1 > file2

To replace the word word1 with the word word2 in the file file1, we can use the sed command:

sed "s/word1/word2/g" file1 > file2

This is often a quicker way to get results than even opening a text editor.

Backup selected files only

• Difficulty: Intermediate
• Application: tar

Want to use tar to backup only certain files in a directory? Then you’ll want to use the -T flag as follows. First, create a file with the file you want to backup:

cat >> /etc/backup.conf
# /etc/passwd
# /etc/shadow
# /etc/yp.conf
# /etc/sysctl.conf
EOF

Then run tar with the -T flag pointing to the file just created:

tar -cjf bck-etc-`date +%Y-%m-%d`.tar.bz2 -T /etc/backup.conf

Now you have your backup.

Read more…….

To encrypt your files use the command:

openssl des3 -salt -in $FILENAME -out ${FILENAME}.des3

To decrypt the file use the command:

openssl des3 -d -salt -in ${FILENAME}.des3 -out ${FILENAME}

You can also use my script ‘tarcrypt.sh’ to encrypt/decrypt files. This script is using tar to compress/decompress with encryption/decryption functionality.

#!/bin/sh
#
# 'tarcrypt.sh' script can used to compress/decompress the data with encryption.
#
# This script is created & tested by Rahul Panwar.
# WARNING!!! Use it at your own risk.
# Please report the bugs or queries to panwar.rahul@gmail.com

VERSION="Version 1.1.0.1nCreated by: Rahul Panwar"
PASS=""
PASS_OPTION=""
EXT_OPTION=""
COMP_FILE="encrypted_file"

DATA_FILES_ALL=""

# Usage
usage ()
{
	echo "Usage:"
	echo "	${0##*/} -c " [  ... "  [-p ]"
	echo "	${0##*/} -x  [-C ] [-p ]"
	echo "	${0##*/} -h"
	echo "	${0##*/} -v"
	echo "OPTIONS:"
	echo "	-c|--compress	: Compress and encrypt the file(s) or directory(ies)
					for multiple files use double quotes (for example "file1 file2 dir1")."
	echo "	-x|--decompress	: Decrypt and uncompress the file"
	echo "	-p|--password	: Password to encrypt/decrypt the file"
	echo "	-C|--extract	: Change directory, to extract the compressed file, default is current directory"
	echo "	-h|--help	: To see this help"
	echo "	-v|--version	: Check the version"
}
[ $# = 0 ] && usage && exit 1

# to encrypt files using openssl
encrypt_file()
{
	FNAME=$1

	#openssl des3 -salt -in "$FNAME" -out "$FNAME.des3"
	openssl des3 -salt -out "$FNAME" ${PASS_OPTION}
}

# to decrypt the files using openssl
decrypt_file()
{
	FNAME=$1

	#openssl des3 -d -salt -in "$FNAME" -out "${FNAME%.[^.]*}"
	openssl des3 -d -salt -in "$FNAME" ${PASS_OPTION}
}

# compress and encrypt the files
en_comp()
{
	tar -czp ${DATA_FILES} | encrypt_file ${COMP_FILE}
}

# decrypt and uncompress the files
de_comp()
{
	decrypt_file ${COMP_FILE} | tar ${EXT_OPTION} -xz
}

# main function
main_function()
{
	compress=""
	decompress=""
	extract=""
	password=""
	while test "$1" != "" ; do
		OPT=$1
		OPT_VAL1=$2
		OPT_VAL2=$3
		case "$OPT" in
			--compress|-c)
				DATA_FILES_ALL="${OPT_VAL1}"
				[ ! "${OPT_VAL2}" ] && echo -e "No encrypt filename, using default name: ${COMP_FILE}"
				COMP_FILE=${OPT_VAL2:-$COMP_FILE}
				compress=1
				shift
				[ "$OPT_VAL2" ] && shift
			;;
			--decompress|-x)
				COMP_FILE=${OPT_VAL1:-$COMP_FILE}
				decompress=1
				shift
			;;
			--password|-p)
				PASS=${OPT_VAL1}
				[ "$PASS" ] && password=1 && PASS_OPTION="-pass pass:${PASS}"
				shift
			;;
			--extract|-C)
				[ ! -d "$OPT_VAL1" ] && echo -e "Extract directory not exists" && exit 1
				EXT_OPTION="-C ${OPT_VAL1:-$PWD}"
				extract=1
				shift
			;;
			--help|-h)
				usage
				exit 0
			;;
			--version|-v)
				echo -e "${VERSION}"
				exit 0
			;;
			-*)
				echo "Error: no such option $OPT"
				usage
				exit 1
			;;
			*)
				echo -e "Error: invalid option $OPT"
				usage
				exit 1
		esac
		shift
	done

	if [ "$compress" ] && [ "$decompress" ]; then
		echo -e "n-c and -x can't be used simultaneouslyn" && usage && exit 1
	elif [ "$extract" ] && [ "$compress" ]; then
		echo -e "n-C can only use with -x optionn" && usage && exit 1
	fi
}

main_function "$@"
if [ "$compress" ]; then
	for FILES in ${DATA_FILES_ALL}; do
		[ -e "${FILES}" ] && DATA_FILES="${DATA_FILES} ${FILES}"
	done
	if [ ! "${DATA_FILES}" ]; then
		echo -e "No file(s) found to compress" && exit 2
	fi
	echo "==> compressing"
	en_comp &>/dev/null && echo "success" || echo "failure"
elif [ "$decompress" ]; then
	[ ! -e "${COMP_FILE}" ] && echo -e "No file to decrypt" && exit 2
	echo "==> decompressing"
	de_comp &>/dev/null && echo "success" || echo "failure"
fi

If you found any bug in the script, please write your comment. I like to improve this, so suggestions are most welcome.