1.1-Introduction to Linux Commands

7/28/2019 1.1-Introduction to Linux Commands

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Introduction to Linuxcommands


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Linux commands

man -- displays manual pages.If you do not know about a command xx

then type $man xx at the command

prompt $. ls -- List the files and directories in the

current directory.

man ls -- show the manual pages about ls cat first.c -- displays contents of the file

first.c


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Linux commands

What does $man man do ?


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Commands

Many commands take one or more

arguments.

$cc first.c -- here cc is the command

first.c is the argument.

Arguments gives the necessary data source

or destination.

$cp a.out first -- copies the file a.out into afile with name first


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Commands

A command can be tailored by giving someoptions.

$ls -l -l is the option, asking for long

display of the file information. It displaysalong with files, the time of their creations,owner, permissions, etc.

$rm temp.c removes the file temp.c This is dangerous. $rm -i temp.c removes, but before doing this

it asks you to confirm.


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Commands

Manual pages gives you all information about

options, arguments.


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File system

The operating system supports a system

called file system whose objectives are to

create, maintain and delete the user/system

information in the form of files. Files can be bundled in the form

directories/folders.

In Linux there is only one file system whichmaintains the files of all users.


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File system

etc

bin

usr

usr1 usr2

Root directory


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File system

Every user will have a home directory.

When the user logs into the system, he/she is

placed at his/her home directory.

Present working directory is the directory

where you are working at present.

$pwd -- displays the present working

directory.


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File system

Navigating the file system.

$cd dir1 -- moves the present working directory to

the directory dir1 (if at all dir1 is present in the pwd,

otherwise it gives an error message) $cd .. -- moves to the parent directory (i.e.,

moves backwards)

$mkdir dir1 -- creates a directory with name dir1

in the pwd. $rmdir dir1 -- removes an empty directory dir1.


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File permissions

You cannot read many other files which are

existing on the system.

The files are protected against misuse.

Every file has 3 category of users User (that is you who created the file)

Group (your group, this group is decided by the

administator) Others (all others)


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File permissions

For every category of users there are 3

possible actions with a file Read (r)

Write (w) (with this you can delete the file also !) Execute (x)

You can modify the file permissions by using

a command chmod Read about this in the manual pages/other

books.


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This lecture gave you a tip of an iceberg.

Read/explore to know more about your

system !

1.1-Introduction to Linux Commands

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