All commands

Easily list all users

Filter comments and empty lines in files. I find this very useful when trying to find what values are actually set in a very long example config file.

I often set an alias for it, like :

alias nocomment='grep -v "^\($\|#\)"'

!$ recalls the last argument of the previous command. This is very useful when you have to operate several operations on the same file for example.

The $2, $3, $4 fields are arbitrary but note that the first field starts from $2 and the last field is $NF-1. This is due to the fact that the leading and trailing quotes are treated as field delimiters.

KDE4 is great, but still a bit buggy, and sometimes plasma requires to be restarted. Instead of quitting it with "killall plasma", which might loose your preferences (widgets, etc.), kquitapp will cleanly quit it. Tip: you can type this in the "Alt+F2" window, and then type "plasma" in Alt+F2 again to restart plasma (be patient though...).

See which files differ in a diff, and how many changes there are. Very useful when you have tons of differences.

I know its not much but is very useful in time consuming scripts (cron, rc.d, etc).

That "^M" is Ctrl-M, which is a carriage return, and is not needed in Unix file systems.

Where ^V is actually Ctrl-V and ^M is actually Ctrl-M (you must type these yourself, don't just copy and paste this command). ^V will not be displayed on your screen.

only works for freeBSD where ports are installed in /usr/ports

credit to http://wiki.freebsd.org/PortsTasks

The ctrl+v,ctrl+m portion represents key presses that you should do. If you do it successfully you should see a ^M character appear.

deletes first 55 lines; change the 55 to whatever number

changes the PS1 to something better than default.

[username.hostname.last-2-digits-of-ip] (current directory)

gpg command to encrypt a file on the command line.

gpg command to decrypt a previously encrypted file on the command line.

Can be optionally made into an alias:

alias decrypt='gpg --output foo.txt --decrypt foo.txt.pgp'

For quick validation of folder's file-contents (structure not taken into account) - I use it mostly to check if two folders' contents are the same.

-p PID and name of the program

-u on a UDP port.

-t also TCP ports

-o networking timer

-n numeric IP addresses (don't resolve them)

-a all sockets

show phpinfo(); from the command line

This command converts a MySQL query directly into a .csv (Comma Seperated Value)-file.

You can read, add, delete and modify Windows permissions from Linux using smbcacls from the smb-client package.

Very useful set of commands to know when your file system was created.

Sometimes, you have a lot of NFS in the server and you can't or shouldn't use umount -a. Whis this command, you only umount the fs related to the 'string'