LINUX / UNIX COMMANDS FREQUENTLY USED

These are some of the frequently Used Unix Commands which may be of help to you. have a look
Starting and Ending
login: `Logging in'
ssh: Connect to another machine
logout: `Logging out'

File Management
emacs: `Using the emacs text editor'
mkdir: `Creating a directory'
cd: `Changing your current working directory'
ls: `Finding out what files you have'
cp: `Making a copy of a file'
mv: `Changing the name of a file'
rm: `Getting rid of unwanted files'
chmod: `Controlling access to your files'
cmp: Comparing two files
wc: Word, line, and character count
compress: Compress a file

Communication

e-mail: `Sending and receiving electronic mail'

talk: Talk to another user

write: Write messages to another user
sftp: Secure file transfer protocol
 

Information

man: Manual pages
quota -v: Finding out your available disk space quota
ical: `Using the Ical personal organizer'
finger: Getting information about a user
passwd: Changing your password
who: Finding out who's logged on

Printing
lpr: `Printing'
lprm: Removing a print job
lpq: Checking the print queues

Job control
ps: `Finding your processes'
kill: `Killing a process'
nohup: Continuing a job after logout
nice: Changing the priority of a job
&: `What is a background process?'
Cntrl-z: Suspending a process
fg: `Resuming a suspended process'

Commonly Used Linux Commands for you.

Linux comes in several versions. The following commands will help you determine which Linux distro is installed on your host, what’s the version of your Linux kernel, the CPU model, processor speed, etc.


$ cat /etc/issue
$ cat /proc/version
$ cat /proc/cpuinfo

Find the total amount of RAM available on your Linux box and how much is free.


$ free -mto

The command cd.. takes you up one directory level but cd – will move you to the previous working directory. Or use the command pwd to print the full path of the current directory that you can copy-paste later into the shell.


$ cd –
$ pwd

The command history will show a list of all the recently executed commands and each will have an associated number. Use !<number> to execute that command again. Or, if the history is too long, use grep to search a particular command.


$ !<command number>
$ history | grep <some command name>

You can remove any particular command from the shell history by number.


$ history –d <command number>

If you made an error while typing a command name, just enter the correct command name and then use !* to reuse all the previous arguments.


$ <command> !*

Re-run a command but after replacing the text abc in the command with xyz.


$ ^abc^xyz

This will list the size of all sub-folders of a directory in KB, MB or GB.


$ du –sh */

A better version of the ls command that displays file sizes in KB and MB.


$ ls –gho

You can use man <command> to learn more about the syntax of a command but what if you don’t remember the name of the command itself? Use apropos then.


$ apropos <search phrase>

Compare the content of two text files to see what has changed.


$ diff wp-config.php wp-config.php.old

Find lines that are common in any two text files.


$ grep –Fx –f file-A.html file-B.html

Compare the content of two directories recursively.


$ diff –urp /old-wp-directory /new-wp-directory

Find all files under the current directory that are larger than 10 MB in size.


$ find . -size +10M -exec du -h {} ;

Find all files on the system that have been modified in the last 2 days.


$ find . –type f –mtime -2

Find all files on the system that were modified less than 10 minutes ago


$ find . –type f –mmin -10

Find all PHP files that contain a particular word or phrase.


$ find . -name “*.php” -exec grep -i -H “matt mullenweg” {} ;

When copying or moving files, Linux won’t show a warning if you are overwriting an existing file. Therefore always use the –i switch to prevent overwrites.


$ cp –i abc.txt xyz.txt

Backup the content of the current folder into a tarball file using gzip compression.


$ tar zcfv backup.tar.gz /wp-directory/

Find processes with the highest CPU usage. Then use kill –9 pid to kill a process.


$ ps aux | sort -nrk 3 | head

Execute the following command in your Apache logs directory to determine hits coming from individual IP addresses.


$ cat access.log | awk ‘{print $1}’ | sort | uniq -c | sort –n | tail

Monitor hits from Google bots to your website in real-time.


$ tail –f access.log | grep Googlebot

To find all files and web pages on your site that return a 404 error, run the following command in the Apache logs directory.


$ awk ‘$9 == 404 {print $7}’ access.log | uniq -c | sort -rn | head

Find the 100 most popular pages of your site using Apache server logs again.


$ cat access.log | awk ‘{print $7}’ |sort |uniq -c |sort -n |tail -n 100

Quickly find and replace a string in or more files.


$ find . -type f -name “*.php” -exec sed -i ‘s/wordpress/WordPress/’ {} ;