Chapter 7 Basic Commands in Linux.

Commands are used to do specific tasks in linux.Commands are always helpful in Linux administration support and If you are a good “commander” you can do anything in Linux! But its difficult to remember all the available commands , so use the help provided by linux , as mentioned in the previous chapter 🙂

Commands:

Everything on a linux system can be done by typing commands – playing music, browsing, chatting and what not.

Commands can be typed in virtual consoles, pseudo terminals (terminal emulators)

indisage@localhost:~$

$ usually means – logged in as a regular user
# usually means – logged in as root.

Don’t rely completely on the above statement of $ and #. They can be changed by changing the PS1 environment variable.

The Syntax:-

command -space- options -space- arguments
Command : ls , mv, cp
Options : -h , –help, –version, -V
Arguments : anything other than options passed to command

eg: ls -la /usr

Basic Commands:-

ls – -a, -F, -l, -1, -A, -t, -R        : lists the files
cd -> dir, /usr , . , ../, .. , –    : change the directory
cp                                        : copy
mv                                       : move
rm                                       : remove
mkdir,rmdir -> -rf and -p options    : make a directory, remove a directory
more/less                            : file perusal filter for crt viewing, less is opposite of more
cat                                      : concatenate files and print on the standard output
head/tail                             : head-output the first part of files,tail-output the last part of files
find/locate/whereis/type –> -exec, -ok, -print0, -type, -uid, -inum, con?, con*, *.conf, “*.conf”, ?conf*
–> locate searches DB and full path, not just filename, while find is relatime and searches filename — -r , -i, -n
cut -f 1,4,5 -d “:” filename
clear                                   : clear the screen/console
date/cal                              : to display the current date/calender
df                                       : report file system disk space usage
finger                                 : user information lookup program
man                                   : an interface to the on-line reference manuals
nano/joe/vi/ed                    : a text base editor’s
passwd                               : change user password
pwd                                   : displays the present working directory
ifconfig                              : configure a network interface
init                                    : process management daemon
ping                                   : send ICMP ECHO_REQUEST to network hosts
ps                                      : report a snapshot of the current processes.
rm/shred                            : remove files or directories/overwrite a file to hide its contents, and optionally delete it
route                                  : show / manipulate the IP routing table
tracroute                             : traces route to a network host discovering MTU along this path
sudo                                   : execute a command as another user
top                                     : display Linux tasks
touch                                  : change file timestamps
w/who/whoami                   : Show who is logged on and what they are doing
which                                 : locate a command
grep -> -r , -i , -n, -v ; man 7 regex ; egrep = grep -E : print lines matching a pattern
kill                                     : send a signal to a process
talk/write/wall/mail            : send a message to another user
tar/cpio/gzip                       : The GNU version of the tar archiving utility, compress or expand files
split                                    : split a file into pieces

Bash Keyboard Shortcuts :-

Ctrl + A – moves cursor to beginning
Ctrl + E – moves cursor to end
Ctrl + h / backspace – Deletes one character
Ctrl + c – Terminate the current executing command, if any and returns to shell
Ctrl + d – Logout
Ctrl + s – Screenlock
Ctrl + q – Unlock screenlock
Ctrl + w – Deletes last word
Ctrl + u – Deletes entire line
Ctrl + k – Clears command line from cursor position to end of line
Ctrl + y – pastes it back
Ctrl + T – Transpose the character on which the cursor rests and the preceding character.
Esc + T  – Transpose the word on which the cursor rests and the preceding word.
tab – Command / filename completion
Ctrl + R – reverse search on command history
Esc+F or Ctrl + -> – Moves right by a word
Esc+B or Ctrl + <- – Move cursor one word left
Ctrl + f or Right Arrow – Move cursor one position right.
Ctrl+B or Left Arrow – Move cursor one position left.
Alt + . and Esc + . – Picks up the arguments of the previous commands

Using Mouse in text mode:-

Copy:-
Left click – Start the selection
Drag – Select an area
Right Click : End the selection. Copied

Paste:-
Middle mouse button click

Happy Commanding 🙂