View the list of hidden files (files that begin with a period character .)
use -a with ls.
eg. ls -la
cd command tricks
cd followed by nothing will change the directory to your home directory.
cd – : changes working directory to previous one.
cd ~zack: changes working directory to my home directory.
less : can be used to view text files eg. less file-name
file : can be used to get the type of data that a file contains. eg. file file-name
tr : translate range of characters into other range of characters.
eg. Translate characters in lowercase to uppercase. tr [a-z] [A-Z]
eg. Translate character a to b and 2 to 3. tr “a2” “b3” < names.txt
whoami: current user logged in
who: current user logged in
head abc.txt # display the first 10 lines
head -n4 abc.txt # display the first 4 lines of file
head -n-6 abc.txt # display all the lines except the last 6 lines of file
tail abc.txt # display the last 10 lines of the file.
tail -n5 abc.txt # display the last 5 lines of the file.
tail -n+8 abc.txt # display from the 8th line till the last.
top: To see currently running processes and other information like memory and CPU usage with real time updates.
sort: sort the characters
uniq: removes duplicates by comparing the adjacent values
eg. $ sort < sname | uniq > u_sname
bc: it is the calculator program in linux
|Value||Shown in bc as||Shown in Linux Shell as|
|False/No||0||Non – zero value|
cal : it’s the calendar program
Builtin shell variables:
$# : Gives no. of arguments to command.
$0 : Shell script name
$1, $2 : Argument 1 and 2 to script.
$*, $@ : Gives all the arguments to the script.
eg. Script name is abc
abc hello world
echo “No. of args $#”
echo “First arg $1”
echo “Second arg $2”
echo “Script name $0”