UNIX Tutorial Six

Changing the Shell Prompt

The value of the BASH shell prompt is contained in the shell variable PS1. It can be modified by simply changing the value of the variable.

% PS1='value' or "value"

Examples

% PS1='Bom Dia>'

Bom Dia> PS1='`ls`\nHi %'

Some special codes that can be included in the prompt.<\p>

• \d the date (day-of-the-week month day))
• \h the hostname (without the domain)
• \n start a new line
• \u the current username
• \w the working directory
• `command` the ` implies that the command is to be executed.

Other useful UNIX commands  

quota

(In the good old days..) All students are allocated a certain amount of disk space on the file system for their personal files, usually about 100Mb. If you go over your quota, you are given 7 days to remove excess files.

To check your current quota and how much of it you have used, type

% quota -v

df

The df command reports on the space left on the file system. For example, to find out how much space is left on the fileserver, type

% df .

du

The du command outputs the number of kilobyes used by each subdirectory. Useful if you have gone over quota and you want to find out which directory has the most files. In your home-directory, type

% du

compress

This reduces the size of a file, thus freeing valuable disk space. For example, type

% ls -l science.txt

and note the size of the file. Then to compress science.txt, type

% compress science.txt

This will compress the file and place it in a file called science.txt.Z

To see the change in size, type ls -l again.

To uncomress the file, use the uncompress command.

% uncompress science.txt.Z

gzip

This also compresses a file, and is more efficient than compress. For example, to zip science.txt, type

% gzip science.txt

This will zip the file and place it in a file called science.txt.gz

To unzip the file, use the gunzip command.

% gunzip science.txt.gz

file

file classifies the named files according to the type of data they contain, for example ascii (text), pictures, compressed data, etc.. To report on all files in your home directory, type

% file *