10 Frequently Used UNIX / Linux Commands

This short post provides practical examples for ten most frequently used commands in Linux/UNIX. The purpose of this list is to give you a jump-start on some of the common Linux commands.

Tar	#Create a new tar archive tar cvf archive_name.tar dirname/ #Extract from an existing tar archive tar xvf archive_name.tar #View an existing tar archive tar tvf archive_name.tar
Grep	#Search for a given string in a file (case insensitive) grep –i “the” demo_file #Print the matched line along with the 3 lines after it grep –A 3 –i “example” demo_text #Search for a given string in all files recursively grep –r “ramesh” *
Find	#Find files using file-name (case insensitive) find –iname “MyProgram.c” #Execute commands on the files found by the find command find –iname “MyProgram.c” –exec md5sum {} \; #Find all empty files in home directory find ~ -empty
SSH	#Login to remote host ssh –l jsmith remotehost.example.com #Debug ssh client ssh –v –l jsmith remotehost.example.com #Display SSH client version ssh –V
Sed	#Convert the DOS file format to Unix file format sed ‘s/.$//’filename #Print file content in reverse sed –n ‘1!G;h;$p’ thegeekstuff.txt #Add line number for all non-empty-lines in a file sed ‘/./=’ thegeekstuff.txt | sed ‘N; s/\n/ /’
Awk	#Remove duplicate lines using awk awk ‘!($0 in array) { array[$0]; print }’ temp # Print all lines from /etc/passwd that have the same uid and gid awk –F ‘:’ ‘$3 == $4’ passwd.txt # Print only a specific field from a file awk ‘{print $2, $5}’ employee.txt
Vim	#Go to the 143rd line of file vim +143 filename.txt #Go to the first match of the specified vim +/search-term filename.txt #Open file in read-only mode vim –R /etc/passwd
Diff	#Ignore white space while comparing diff –w name_list.txt name_list new.txt
Sort	#Sort a file in ascending order sort names.txt #Sort a file in descending order sort –r names.txt #Sort passwd file by 3rd field sort –t: -k 3n /etc/passwd | more
Export	#View oracle related environment variables export | grep ORACLE #Export an environment variable export ORACLE_HOME = ‘/u01/app/oracle/product/10.2.0’