Some useful commands in Debian 5/6

head and tail shows the first 10 and the last 10 lines of a file respectively


head -n 1 will show the first line and tail -n 1 will show the last line


STDERR 2>error.txt


ls -l sourav 2>> error.txt


will put the error in the file error txt


we can watch the ongoing errors in a different terminal using the command 


watch tail error.txt


file filename returns the type of the file


for example file * shows every file's type that is presented in the directory


wc -l filename shows the number of lines in a file


wc is for word count


seq 50 will show the sequence from 1 to 50


creating a loop in the terminal to print hello couple of times.




for i in `seq 50`;do echo "Hello"; done


or may be like this


for i in `seq 50`;do echo "Hello - $i"; done


suppose we want to see the number of files in a directory using a loop


for i in `ls -a`;do echo "File - $i"; done | wc -l




or may be see the files one by one using a loop


for i in `ls -a`;do echo "File - $i"; done 


reset to create a new buffer(any command will now run on a new buffer after the command reset)




free to see the info about memory


free -m returns the output in a more readable format


kill a process using top


type top


type k


enter the pid of the process