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#!/bin/sh
# Wojtek Jamrozy www.wojtekrj.net
 
if [ $# != 1 ]; then
	echo "usage: $0 <url of website> "
	exit 1
fi
hash=`wget -q -O - $1 | md5sum`
 
while [ 1 ]; do
	if [ "`wget -q -O - $1 | md5sum`" != "$hash" ]; then
		firefox $1
		notify-send "Change on the website $1"
		exit 0
	fi
	echo "Nothing has changed"
	sleep 120
done

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#!/bin/sh
# Author: Wojtek Jamrozy (www.wojtekrj.net)
# BE SURE WHAT ARE YOU DOING - YOU CAN LOST IMPORTANT DATA
 
if [ $# != 1 ]; then
	echo "usage: $0 <name of device>"
	exit 1
fi
 
echo "You choose $1 device to shred"
echo "Are you sure (it will destroy ALL data on this device)? Type upercase yes:"
read yes
TMP_DIR=/tmp/_tmpfs
SIZE=100 # size of pattern in megabytes
if [ "$yes" = "YES" ]; then
	echo "Generating random pattern..."
	mkdir -p $TMP_DIR
	sudo mount -t tmpfs  tmp $TMP_DIR
	dd if=/dev/urandom of=$TMP_DIR/plik bs=${SIZE}MB count=1 2> /dev/null
	echo "Generating random pattern finished..."
	echo "Starting shreding $1"
	before=`date +%s`
	i=0
	while [ 1 ]; do	
		sudo dd if=$TMP_DIR/plik of=$1 bs=${SIZE}MB seek=$i 2> /dev/null
		if [ $? != 0 ]
		then
			break
		fi
		i=$((i+1))
		after=`date +%s`
		echo "$((i*SIZE))MB have been copied\nAverage speed: $((i*SIZE/(after-before+1))) MB/s"
	done
	after=`date +%s`
	echo "Average speed: $(((i+1)*SIZE/(after-before+1))) MB/s"
	rm $TMP_DIR/plik
	sudo umount $TMP_DIR
	rm -R $TMP_DIR
else
	echo "You haven't typed \"YES\"\nExiting..."
fi

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#!/bin/bash 
# passwords.sh  
if [ $# != 2 ]; then
	echo "usage: $0 <length of passwords> <number of passwords> "
	exit 1
fi
tr -cd '[:graph:]' < /dev/urandom | fold -w $1 | head -$2

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#!/bin/bash 
# dd.sh Author: Wojtek Jamrozy (www.wojtekrj.net)
 
dd $* & pid=$!
sleep 10
 
while [ -e "/proc/$pid" ] ; do
	kill -USR1 $pid 
	sleep 10
done

Line 4 executes dd with arguments of dd.sh at the background, and stores PID of dd process in $pid variable
In line 7 while checks if /proc/$pid exists. If exsists, process $pid is still running.
Line 8 is executed every 10 secunds and tell dd to show information about progress.

Example of usage:

$ ./dd.sh if=/dev/zero of=/dev/null count=50000000
11282170+0 przeczytanych recordów
11282169+0 zapisanych recordów
skopiowane 5776470528 bajtów (5,8 GB), 10,0174 s, 577 MB/s
22557922+0 przeczytanych recordów
22557922+0 zapisanych recordów
skopiowane 11549656064 bajty (12 GB), 20,0196 s, 577 MB/s
33852540+0 przeczytanych recordów
33852540+0 zapisanych recordów
skopiowane 17332500480 bajtów (17 GB), 30,0219 s, 577 MB/s
45151438+0 przeczytanych recordów
45151437+0 zapisanych recordów
skopiowane 23117535744 bajty (23 GB), 40,024 s, 578 MB/s
50000000+0 przeczytanych recordów
50000000+0 zapisanych recordów
skopiowane 25600000000 bajtów (26 GB), 44,321 s, 578 MB/s

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#!/bin/sh
for i in `dpkg -l | grep ^rc | cut -f 3 -d ' '`
do
    dpkg -P $i;
done

dpkg -l shows list of packages installed in system
grep ^rc print all lines starting with “rc” (in this case print all lines with name of packages which configuration files are still in system)
cut -f 3 -d ‘ ‘ Divides lines into fields using space as delimiter and prints 3rd field (in this case retrieve name of packages to delete)
dpkg -P package purges package
This link explains other things.
Script can also be added to /etc/crontab as:

09 18 * * * root for i in `dpkg -l | grep ^rc | cut -f 3 -d ' '`; do dpkg -P $i; done

Script will be executed with root privileges everyday at 18:09.

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Here is an example:

#!/bin/sh
 
for i in `seq 0 5 15`
do
	echo $i
done

The output is:

0
5
10
15

seq 0 5 15 iterates from 0 to 15 with step 5

`command` executes command and return its standard output

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nohup program > output

If you close SSH session (or terminal), program will be still executed and standard output of program will be send to output file.

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We have a program, which can suspend our terminal. We want to be sure, that program won’t be executed for more than n seconds. Here is a solution:

((sleep 10 && killall top)&); top

Explanation:
sleep 10 is executed for 10 seconds and then exit (you can use sleep n if you want sleep to be executed for n seconds

killall top terminates all processes named “top”

top - is example of program; top shows information about processes in your system

command1 && command2 – executes command1 and then, if command1 has succedeed, command2

command & – executes command at the background of terminal

command1; command2 – executes command1 and command2, even if command1 hasn’t succedeed

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1,AAAA,NNN
11,BBB,OOO
21,CCC,PPP
12,DDD,RRR
23,EEE,SSS
14,FFF,TTT
14,FFF,TTT
14,FFF,TTT
4,JJJJ,XXX
6,KKKK,YYY
5,LLLL,ZZZ
7,MMMM,AAA

and test2.txt:

1000,aaa,bbb
1000,aaa,bbb

Secondly, when you write:
command1 | command2 | command 3 – the standard output of command1 is the standard input of command2 and the standard output of command2 is the standard input of command3

wojtekrj@wojtek-laptop:~$ echo "test" | cat
test

command1 && command2 – if command1 is successfully executed, system will execute command2

command1 < infile > outfile – content of infile is standard input of command1 and the output of command1 is saved to outfile

wojtekrj@wojtek-laptop:~$ cat < test.txt > test3.txt && cat test3.txt
1,AAAA,NNN
11,BBB,OOO
21,CCC,PPP
12,DDD,RRR
23,EEE,SSS
14,FFF,TTT
14,FFF,TTT
14,FFF,TTT
4,JJJJ,XXX
6,KKKK,YYY
5,LLLL,ZZZ
7,MMMM,AAA

The file will be used to show working of commands:

cat – without arguments it just copies standard input to standard output (if you use keyboard as standard input, type Ctrl+D when you finish – cat will treat it as EOF (end of file) character). If it has one argument, it will print content of file, which name is the first argument. If it has more arguments, it will print contents of files in order they apeared as arguments.

wojtekrj@wojtek-laptop:~$ cat test.txt
1,AAAA,NNN
11,BBB,OOO
21,CCC,PPP
12,DDD,RRR
23,EEE,SSS
14,FFF,TTT
14,FFF,TTT
14,FFF,TTT
4,JJJJ,XXX
6,KKKK,YYY
5,LLLL,ZZZ
7,MMMM,AAA
wojtekrj@wojtek-laptop:~$ cat test2.txt
1000,aaa,bbb
1000,aaa,bbb
wojtekrj@wojtek-laptop:~$ cat test.txt test2.txt
1,AAAA,NNN
11,BBB,OOO
21,CCC,PPP
12,DDD,RRR
23,EEE,SSS
14,FFF,TTT
14,FFF,TTT
14,FFF,TTT
4,JJJJ,XXX
6,KKKK,YYY
5,LLLL,ZZZ
7,MMMM,AAA
1000,aaa,bbb
1000,aaa,bbb

tac – it works like cat, but prints lines of files in reversed order

wojtekrj@wojtek-laptop:~$ tac test.txt
7,MMMM,AAA
5,LLLL,ZZZ
6,KKKK,YYY
4,JJJJ,XXX
14,FFF,TTT
14,FFF,TTT
14,FFF,TTT
23,EEE,SSS
12,DDD,RRR
21,CCC,PPP
11,BBB,OOO
1,AAAA,NNN
wojtekrj@wojtek-laptop:~$ tac test.txt test2.txt
7,MMMM,AAA
5,LLLL,ZZZ
6,KKKK,YYY
4,JJJJ,XXX
14,FFF,TTT
14,FFF,TTT
14,FFF,TTT
23,EEE,SSS
12,DDD,RRR
21,CCC,PPP
11,BBB,OOO
1,AAAA,NNN
1000,aaa,bbb
1000,aaa,bbb

uniq – it prints content of file without subsequent same lines

wojtekrj@wojtek-laptop:~$ uniq test.txt
1,AAAA,NNN
11,BBB,OOO
21,CCC,PPP
12,DDD,RRR
23,EEE,SSS
14,FFF,TTT
4,JJJJ,XXX
6,KKKK,YYY
5,LLLL,ZZZ
7,MMMM,AAA
wojtekrj@wojtek-laptop:~$ uniq test2.txt
1000,aaa,bbb

sort – it sorts lines of file in lexicographical order. If command is executed with -n option, it will compare numbers at the begining of each line.

wojtekrj@wojtek-laptop:~$ sort test.txt
11,BBB,OOO
12,DDD,RRR
14,FFF,TTT
14,FFF,TTT
14,FFF,TTT
1,AAAA,NNN
21,CCC,PPP
23,EEE,SSS
4,JJJJ,XXX
5,LLLL,ZZZ
6,KKKK,YYY
7,MMMM,AAA
wojtekrj@wojtek-laptop:~$ sort -n test.txt
1,AAAA,NNN
4,JJJJ,XXX
5,LLLL,ZZZ
6,KKKK,YYY
7,MMMM,AAA
11,BBB,OOO
12,DDD,RRR
14,FFF,TTT
14,FFF,TTT
14,FFF,TTT
21,CCC,PPP
23,EEE,SSS

nl - add a number before each line of file

wojtekrj@wojtek-laptop:~$ nl  test.txt
1	1,AAAA,NNN
2	11,BBB,OOO
3	21,CCC,PPP
4	12,DDD,RRR
5	23,EEE,SSS
6	14,FFF,TTT
7	14,FFF,TTT
8	14,FFF,TTT
9	4,JJJJ,XXX
10	6,KKKK,YYY
11	5,LLLL,ZZZ
12	7,MMMM,AAA

head – prints first 10 lines of file. If it is executed with option -N, when N is a number, it will print first N lines of file

wojtekrj@wojtek-laptop:~$ head test.txt
1,AAAA,NNN
11,BBB,OOO
21,CCC,PPP
12,DDD,RRR
23,EEE,SSS
14,FFF,TTT
14,FFF,TTT
14,FFF,TTT
4,JJJJ,XXX
6,KKKK,YYY
wojtekrj@wojtek-laptop:~$ head -3 test.txt
1,AAAA,NNN
11,BBB,OOO
21,CCC,PPP
wojtekrj@wojtek-laptop:~$ head -1 test.txt
1,AAAA,NNN

tail – similar to head, but prints last lines

wojtekrj@wojtek-laptop:~$ tail test.txt
21,CCC,PPP
12,DDD,RRR
23,EEE,SSS
14,FFF,TTT
14,FFF,TTT
14,FFF,TTT
4,JJJJ,XXX
6,KKKK,YYY
5,LLLL,ZZZ
7,MMMM,AAA
wojtekrj@wojtek-laptop:~$ tail -3 test.txt
6,KKKK,YYY
5,LLLL,ZZZ
7,MMMM,AAA
wojtekrj@wojtek-laptop:~$ tail -1 test.txt
7,MMMM,AAA

wc - it counts number of characters, words and lines of file. It can print statistics only for characters (option -c), words (-w) and lines (-l).

wojtekrj@wojtek-laptop:~$ wc test.txt
12  12 132 test.txt
wojtekrj@wojtek-laptop:~$ wc -w test.txt
12 test.txt
wojtekrj@wojtek-laptop:~$ wc -l test.txt
12 test.txt
wojtekrj@wojtek-laptop:~$ wc -c test.txt
132 test.txt

tr – read content from standard input and write to standard output deleting or changing some characters:
tr string1 string2 replaces first character from string1 to first character from string2, second to second, third to third, etc.
tr -d string1 deletes every occurrence of characters from string1
tr -cd string1 deletes every occurence of characters, which are NOT from string1

wojtekrj@wojtek-laptop:~$ cat test2.txt | tr abc ABC
1000,AAA,BBB
1000,AAA,BBB
wojtekrj@wojtek-laptop:~$ cat test2.txt | tr -d abc
1000,,
1000,,
wojtekrj@wojtek-laptop:~$ cat test2.txt | tr -cd abc
aaabbbaaabbb

cut – prints only part of line. Each line is constructed of fields separated by special character called separator.
Let’s consider line:

1,AAAA,NNN

The separator is character “,”, there are 3 fields: first – “1″, second – “AAAA” and third “NNN”. cut has following syntax:
cut -d C -f N text.txt where C is separator and N is number of field to display

wojtekrj@wojtek-laptop:~$ cut -d , -f 1-2 test.txt
1,AAAA
11,BBB
21,CCC
12,DDD
23,EEE
14,FFF
14,FFF
14,FFF
4,JJJJ
6,KKKK
5,LLLL
7,MMMM
wojtekrj@wojtek-laptop:~$ cut -d , -f 1,3 test.txt
1,NNN
11,OOO
21,PPP
12,RRR
23,SSS
14,TTT
14,TTT
14,TTT
4,XXX
6,YYY
5,ZZZ
7,AAA

If you write after -f N-M fields from N to M will be printed. If N,M – N-th and M-th field will be printed.

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#!/bin/sh
# Created by Wojtek Jamrozy (www.wojtekrj.net)
mv $1 cop_$1
mv $2 $1
mv cop_$1 $2

Note: There is a file embedded within this post, please visit this post to download the file.
Download this file or make a text file with this content named swap and make it executable with command

chmod +x swap

Then copy this file to /usr/local/bin directory using:

cp swap /usr/local/bin

If you have this file in /usr/local/bin directory (or any other included in $PATH environment variable – command

echo $PATH

will show other directories) you don’t have to write full path to script:

swap f1 f2

will swap contents of files f1 and f2.
Example of usage in shell:

wojtekrj@wojtek-laptop:~$ echo "File 1" > file1 && echo "File 2" > file2
wojtekrj@wojtek-laptop:~$ cat file1
File 1
wojtekrj@wojtek-laptop:~$ cat file2
File 2
wojtekrj@wojtek-laptop:~$ swap file1 file2
wojtekrj@wojtek-laptop:~$ cat file1
File 2
wojtekrj@wojtek-laptop:~$ cat file2
File 1

#!/bin/sh

is a standard header, which helps bash shell recognize file as a bash script.

mv file1 file2

a command, which rename/move file from path file1 to file2

cat file

show content of file

When the script is executed with two arguments (like in example – swap f1 f2), $1 will contain first argument – f1, and $2 second – f2.
When $1 or $2 appears in script, it’s replaced with content of $1 or $2:

mv $1 cop_$1 -> mv f1 cop_f1
mv $2 $1 -> mv f2 f1

echo text_to_display

echo "text_to_display"

commands will show text text_to_display

command > file

will save output of command to file file

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