Frequently Use Unix Commands

List Command: ls

The ls command shows a list of files in the present directory.

For example:

[oracle@localhost ~]$  ls

Desktop  oraInventory  Screenshot.png

If the ls commands is use with  -l option it would help to get more information about the listed files.

For example:

[oracle@localhost ~]$  ls -l

total 148

drwxr-xr-x    2  oracle  oinstall   4096     Jun 30 09:35  Desktop

drwxrwx---   6  oracle  oinstall   4096     Jun 30 09:45   oraInventory

-rw-r--r--      1  oracle  oinstall 128924   Jul  1 00:18    Screenshot.png

First Column: represents file type and permission given on the file. Below is the description of all type of files.

Second Column: represents the number of memory blocks taken by the file or directory.

Third Column: represents owner of the file. This is the Unix user who created this file.

Fourth Column: represents group of the owner. Every Unix user would have an associated group.

Fifth Column: represents file size in bytes.

Sixth Column: represents date and time when this file was created or modified last time.

Seventh Column: represents file or directory name.

Unix Meta Characters

Meta characters have special meaning in Unix. For example * and ? are meta characters. We use

* to match 0 or more characters, a question mark ? matches with single character.

For example:

[oracle@localhost dbs]$  ls *.ora

initdw.ora  init.ora  spfileorcl.ora

Unix Hidden Files

An invisible file is one whose first character is the dot or period character (.). UNIX programs

(including the shell) use most of these files to store configuration information.

Creating and Editing Files

Vi editor:

It is use to create or edit ordinary files on any Unix system.

[oracle@localhost ~]$ vi filename

After this press i for editing the file. For saving the file press Esc then Shift+: and wq!. Exit saving the file.

Display Content of a File

Cat Command:

It is use to see the content of a file.

[oracle@localhost ~]$ cat filename

The above command will display the contents of the filename file.

Copying Files

Cp Command: It is use to make a copy of a file. The basic syntax of the command is:

[oracle@localhost ~]$  cp source_file destination_file

The above command copy the contents of source_file to the destination_file

Renaming or Moving File

mv command: To change the name of a file use the mv command. Its basic syntax is:

[oracle@localhost ~]$  mv old_file new_file

Following is the example which would rename existing file filename to newfile:

[oracle@localhost ~]$  mv filename newfile

Deleting Files:

Rm command: To delete an existing file use the rm command. Its basic syntax is:

[oracle@localhost ~]$ rm filename

You can remove multiple files at a tile as follows:

[oracle@localhost ~]$ rm  filename1  filename2  filename3