Linux Training

Session II

Basic CommandsBy

Gourav Shahhttp://freedomyug.wordpress.com/

Topics

Command Line Basics

Working with directories

File Manipulations

Command Line Basics

Shell Variables

Executing Commands

Command sequences

Command history

Applying commands recursively

Shell Variables

Shell Variable - a named storage location that contains a value

Bash maintains a set of shell variables which contain imp info for execution of bash

e.g. $PS1 , $PATH

Environment Variables – shell variables used during the execution of the programs.

Setting up environment variable

e.g export MYVAR

Executing Commands

Anatomy of a command,

cp -r abc xyz

“cp” : a valid command “-r” : command option / switch “abc , xyz” : arguments

e.g. ls -al

Command Sequences

How to enter multiple commands on a single line ?

Ans. use command separator ( ; ) after each command except the last one

e.g. ls ; ps

Command History History is useful to repeat/modify long and

complex command sequences executed in the recent past.

Command history expansion designators,!! : most recent command!n : refer to command 'n' from history. Use

command history to find out n!-n : current command -n!string: most recent command starting with

string!? : most recent command containing string

Applying Commands Recursively

Using wildcards e.g. chmod +x *.sh

Recursive option -r -R --recursive e.g. chmod -R tmp

Inherently recursive commands e.g. Find /home/ses -name “*.txt”

Working with directories

Listing contents of the working directory

Creating directories

Moving in directories

Removing directories

Listing Contents of a Directory

Command : ls Description : list directory contents

Options -a, --all : list entries including hidden files (.xx)-l : use long listing format

e.g. ls ls -l ls -l -all ls -al

Creating Directories

Command: mkdirDescription: create one or more directoriesoptions:-m : set access mode for dirs-p : create parent dir if it doesn't exist

e.g mkdir amar mkdir akbar anthony mkdir -p amar/akbar/anthony mkdir -m 777 movie

Moving in Directories

Command : cdDescription: change working directory

Command : pwdPurpose: print working directorye.g. cd abc cd /home/ses/abc ( absolute path) pwd cd .. ( move to parent dir)

Removing Directories

Command : rmdirDescription: removes empty directoriesOption: -p : removes dirs and parent dirs

e.g.

rmdir -p amar/akbar/anthonyrmdir akbar

File Manipulations

Display file – more, less, cat

Copy file – cp

Rename/Move file – mv

Remove files - rm

Find file – find

Copying files between machines – scp, rsync

Displaying Files

Commands : less, moreDescription: output text one screen at a time

e.g more blah-blah.txt less blah-blah.txt

Command : catDescription: concatenate files and print on the

standard output

e.g cat blah-blah.txt

Copying Files

Command: cpDescription: copy files and directoriesOptions: -f : force an overwrite-r, -R : recursive copy-v : verbose Syntax : cp [options] source dest

e.g. mkdir home office touch home/room.txt cp home/room.txt office/

Renaming/Moving Files

Command: mvDescription: rename/move files Syntax: mv [options] src dest

e.g. Renaming a file

touch rajnimv rajni the_boss

Moving a filemv the_boss movies/

Removing Files

Command : rmDescription : remove files or directoriesOptions:-f , --force : force remove-r , -R : recursive (remove dir contents)-v : verbosee.g.

rm foo.txtrm -rf /home/ses/foo/*

***always be careful when using rm command

Finding Files

Command : findDescription: search for files in a directory

hierarchySyntax : find [path] [expression]

e.g.

find /home/ses/ -name “*.py”

Remote File Manipulation

Command : scpDescription: secure copy (remote copy program)Options: -r : recursiveSyntax: scp [options] src dest

If src/dest is remote then use 'user@host:path'

e.gscp foo ses@zene:/home/ses/scp release@brownback:~/foobar.csv /home/ses/

Remote File Manipulation

Command: rsyncDescription: copies files to or from a remote

host. Transfers only differences between two sets of files.

Options: -a : archive, preserver everything-v : verbose-z : compression

Syntax: rsync [options] src dest'user@host:path' for the remote machinee.g. rsync -avz /src/bar ses@zene:/tmp rsync -avz /src/bar/ ses@zene:/tmp