UNIX is open source software that was originally created by Ken Thompson at Bell Labs way back in 1969. As time goes by, it has been developed in to a variety of distros also known as unix flavours. Some of the flavours that were derived by volunteers remain free while others are not. Linux is a known free unix derivative that has gone far enough which made it as an alternative to proprietary operating systems and now being widely use in several industries.


10 Basic UNIX / LINUX Commands

I’ve listed here10 basic UNIX commands that will help you get started in your venture of playing around the UNIX world. These commands are applicable in Linux, Solaris & other distros.

Suggestion:

To know more about the commands, access the manual page by typing man <command> on the command prompt.

Example:
10 Basic UNIX / LINUX Commands

1. sudo
 This is to execute a command as another user.

SYNOPSIS

sudo -V | -h | -l | -L | -v | -k | -K | -s | [ -H ] [-P ] [-S ] [ -b ] | [ -p prompt ] [ -c class|- ] [ -aauth_type ] [ -u username|#uid ] command

DESCRIPTION

sudo allows a permitted user to execute a command as the superuser or another user, as specified in the sudoers file. The real and effective uid and gid are set to match those of the target user as specified in the passwd file (the group vector is also initialized when the target user is not root). By default, sudo requires that users authenticate themselves with a password (NOTE: by default this is the user's password, not the root password). Once a user has been authenticated, a timestamp is updated and the user may then use sudo without a password for a short period of time (5 minutes unless overridden in sudoers).

EXAMPLES

Command
Explanation
Sudo –u root –i
To switch to root user
Sudo  -l
To see what sudo permissions the user has

2. mkdir
 Make directory

SYNOPSIS

mkdir [OPTION] DIRECTORY...  

DESCRIPTION

Create the DIRECTORY(ies), if they do not already exist.

EXAMPLES

Command
Explanation
Mkdir scripts
To create directory named scripts
Mkdir /tmp/files
To create folder under  tmp directory

3. cd
Change working directory

SYNOPSIS

     /usr/bin/cd [directory]

DESCRIPTION

       The /usr/bin/cd utility changes the current directory in the context of the cd utility only. This is in contrast to the version built into the shell. /usr/bin/cd has no effect  on
The invoking process but can be used to determine whether or not a given directory can be set as the current directory.

EXAMPLES

Command
Explanation
Cd scripts
To open script directory you’ve created in #2

4. pwd
- return working directory name

SYNOPSIS

     /usr/bin/pwd

DESCRIPTION

     The pwd utility writes an absolute path name of the current working directory to standard output.

EXAMPLE

Command
Explanation
Pwd
To your current working directory.

5. Vi
Screen-oriented (visual) display editor  based on ex

SYNOPSIS

vi [ -| -s ] [-l] [-L] [-R] [ -r [ filename ] ] [-S] [-t tag] [-v] [-V] [-x] [-w] [-n ] [-C] [+command | -c command ] filename

EXAMPLE

Command
Explanation
vi myfile.txt
To create or edit a text file
:q!
To quit without saving
:wq!
To save and quit the file

To know more about vi editor - http://www.cs.rit.edu/~cslab/vi.html

 6. ls
list contents of directory

SYNOPSIS

     ls  [options] file

DESCRIPTION

     For each file that is a directory, ls list the contents of the directory.  For each file that is an ordinary file, ls repeats its name and any other information requested.  The output is sorted alphabetically by default. When no argument is given, the current directory (.) is listed. When several arguments   are   given, the arguments are first sorted appropriately, but file arguments appear before directories.

EXAMPLE

Command
Explanation
Ls -lrts
To long list files inside your current working directory.
Ls -la
To long list hidden files.

7. chmod
Change the permissions mode of a file.

SYNOPSIS

    chmod [option] file

DESCRIPTION
    
The chmod utility changes or assigns the permissions of a file.
U= user/owner
G  =group
O = others
A = all users
R = read = 4
W = write = 2
X = execute = 1

EXAMPLE

Command
Explanation
Chmod 777 myfile.txt
To change permission of myfile.txt into readable writable & executable for all users.
Chmod o+x myfile.txt
To change grant other users with execute permission.

To know more about chmod command - http://www.ss64.com/bash/chmod.html

8. rm
- remove directory entries

SYNOPSIS

rm [options] file

DESCRIPTION

The rm utility removes the directory entry specified by each file argument.  If a file has no write permission and the standard input is a terminal, the full  set  of  permissions (in  octal)  for the file are printed followed by a question mark. This is a prompt for confirmation.  If the answer begins  with y (for yes), the file is deleted, otherwise the file remains.

EXAMPLE

Command
Explanation
Rm myfile.txt
To delete/remove myfile.txt

9. find
 find files

SYNOPSIS

     find [-H |  -L] path... expression

DESCRIPTION

     The find utility recursively descends the directory hierar- chy for each path seeking files that match a Boolean expres-sion written in the primaries given below.
find is able to  descend  to  arbitrary  depths  in  a  file hierarchy  and  does not fail due to path length limitations (unless a path operand specified by the application  exceeds PATH_MAX requirements).

EXAMPLE

Command
Explanation
Find /scripts ‘myfile.txt’
To find myfile.txt inside /scripts directory.
Find . –type f –name ‘myfile.txt’
To find myfile.txt into current working directory.

10. mv
move (rename) files

SYNOPSIS

       mv [OPTION]... [-T] SOURCE DEST
       mv [OPTION]... SOURCE... DIRECTORY
       mv [OPTION]... -t DIRECTORY SOURCE...

DESCRIPTION

       Rename SOURCE to DEST, or move SOURCE(s) to DIRECTORY.

EXAMPLE

Command
Explanation
Mv myfile.txt hisfile.txt
Rename myfile.txt to hisfile.txt
Mv /scripts/myfile.txt  /tmp/
To move myfile.txt from scripts directory to tmp directory.

Next post will be about troubleshooting of common unix issues. Please share your unix related experiences as well. J
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