Parrot OS Basics 1.5

Some Tricks and Tips

In this blog post, we will learn the tricky usage of some commands and utilities.

cat command

To add text and make a file

$ cat > filname.py or filename.txt or filename.c

To append text in a file

$ cat » filename.java or filename.sh .

To number line in the output

$ cat -n filename.txt

alias command

$ alias (to list all alias)

To set alias

$ alias hi=’echo “hi hacker” ‘

Now write hi on terminal and press enter, it will show

$ hi
hi hacker

Now another command

$ alias scanme=’nmap -sS -p- localhost’

Run scanme and you will Nmap scan result for your system

$ scanme

$ alias scanmehard=’nmap -A -p- localhost’

you can set multiple alias like this

To permanently add them into your profile, you just need to append the above commands in .bashrc, like below.

$ nano ~/.bashrc

append the above line at the end of the file and relaunch terminal.

Use shopt -s cdspell to automatically correct your typos

$ shopt -s cdspell $ cd /hme
try this it will cd to home

grep command

print lines that match patterns

example :

$ grep root /etc/passwd

Option -v, will display all the lines except the match

$ grep -v root /etc/passwd

count lines match

$ grep -c root /etc/passwd

count lines don’t match

$ grep -cv root /etc/passwd

search ignoring case

$ grep -i root /etc/passwd

find command

Search for files in a directory hierarchy

Syntax: find [pathnames] [conditions]

find files containing a specific word in its name

find /home -name “hacker”

find all the files greater than certain size

find / -type f -size +500M

sort, uniq, diff, fmt commands

sort - sort lines of text files

$ sort filename.txt

fmt - format unformated file

$ fmt hacker.txt

uniq - omit repeated lines

$ uniq hackerrepeat.txt

diff - compare files line by line and report the difference

$ diff [options] file1 file2

awk command

Awk is a programming language that allows easy manipulation of structured data and the generation of formatted reports.

Basic Syntax

$ awk ‘/search pattern1/ {Actions}

/search pattern2/ {Actions}’ file

Print the lines which matches with the pattern.

$ awk ‘/hacker/

> /hactivist/’ badactors.txt

Initialization and Final Action

Awk has two important patterns that are specified by the keyword called BEGIN and END.

$ awk ‘BEGIN {print “Name\tcrime\tplace\tmoney”;}

> {print $2,”\t”,$3,”\t”,$4,”\t”,$NF;}

> END{print “Report Generated\n————–”;

> }’ badactors.txt

wget and curl commands

you can download files using wget and curl from internet

example

$ wget https://github.io/uname/tools.git

$ curl https://github.io/uname/tools.git

I/O Redirection

Input and output in the Linux environment is distributed across three streams

stdin (0)

stdout (1)

stderr (2)

Commands with a single bracket overwrite the destination’s existing contents.

Overwrite

> - standard output

< - standard input

2> - standard error

Commands with a double bracket do not overwrite the destination’s existing contents.

Append

>> - standard output

« - standard input

2» - standard error

Pipes are used to redirecting a stream from one program to another

example

filters used by pipe

find - Find returns files with filenames that match the argument passed to find.

grep - Grep returns text that matches the string pattern passed to grep.

tee - Tee redirects standard input to both standard output and one or more files.

tr - tr finds-and-replaces one string with another.

wc - wc counts characters, lines, and words.

Conclusion

These are very useful command tricks of Linux, use them.