10 Most Frequently Used Linux Commands

Are you starting out on the Linux command line? Are you having a hard time remembering those commands? Not to worry. Here's a list of some of the most common and most basic commands that are used on Linux, along with some examples explaining there usage

1. tar command

   The following command creates a new tar archive:

   tar cvf archive_name.tar dirname/
   

   Use this when you need to extract from an existing archive:

   tar xvf archive_name.tar
   

   This is the command that is used to view a tar archive:

   tar tvf archive_name.tar
   

2. grep command

   This command searches for a given string within a file:

   grep -i "the" demo_file
   

   This command prints a matched line and three lines after it:

   grep -A 3 -i "example" demo_text
   

   Recursively search for a string in all files:

   grep -r "ramesh" *
   

3. find command

   Use this to find files when the filename is known:

   find -iname "MyCProgram.c"
   

   This command is used to execute command on files that have been found using find:

   find -iname "MyCProgram.c" -exec md5sum {} \;
   

   Empty files in the directory:

   find ~ -empty
   

4. ssh command

   This command allows you to login to a remote host.

   ssh -l jsmith remotehost.example.com
   

   Use this to debug ssh clients:

   ssh -v -l jsmith remotehost.example.com
   

   For displaying the ssh client version:

   ssh -V
   

5. sed command

   Convert the DOS file format into Unix format:

   sed 's/.$//' filename
   

   Print the contents of a file in reverse order:

   sed -n '1!G;h;$p' thegeekstuff.txt
   

   Add a line number for the non-empty lines in a particular file

   sed '/./=' thegeekstuff.txt | sed 'N; s/\n/ /'
   

6. awk command

   Remove duplicate lines:

   awk '!($0 in array) { array[$0]; print }' temp
   

   Print all lines from a file , which have the same uid and gid:

   awk -F ':' '$3==$4' passwd.txt
   

   Printing specific fields from a particular file:

   awk '{print $2,$5;}' employee.txt
   

7. vim command

   Go to the file's 143rd line.

   vim +143 filename.txt
   

   Go to the first found match of the file specified:

   vim +/search-term filename.txt
   

8. diff command

   Ignoring white spaces when comparing files:

   diff -w name_list.txt name_list_new.txt
   

9. sort command

   Ascending order:

   sort names.txt
   

   Descending order:

   sort -r names.txt
   

   Sort a file (passwd) the third field:

   sort -t: -k 3n /etc/passwd | more
   

10. export command

    Use this for viewing oracle related environment variables:

    export | grep ORACLE
    declare -x ORACLE_BASE="/u01/app/oracle"
    declare -x ORACLE_HOME="/u01/app/oracle/product/10.2.0"
    declare -x ORACLE_SID="med"
    declare -x ORACLE_TERM="xterm"
    

    Export environment variable:

    export ORACLE_HOME=/u01/app/oracle/product/10.2.0