Remembering the basics – Week 1

Dan Morrill April 01 2013

CIS 216 – Shell Scripting

RMDIR – removes a directory only if it is empty

RMDIR –r – removes a directory regardless if it is empty or not

CHMOD 777 –r /user/dan – recursively changes the permissions of the directory /user/dan to RWXRWXRWX

grep – pattern matching for example ps –ef |grep apache2 will look for all processes running under the name apache2egrep – used in regular expressions

Remembering the basic Unix Commands

find – find the location of a file (or files) on a hard drive at the command line

echo – writes data to the screen (standard output)The TTY – Screen is always standard output

(STDOUT)more – displays the contents of a file one

page at a time (hard for long files like syslog)clear – clears the screen of text and provides

the command prompt chown – change the owner of a file or

directoryrm – remove a file

Remembering the basic Unix Commands

mv – move a file to a new place and or new namechgrp – change the group ownership of a filemkdir – make a directoryls – list the files in a directory, ls –la show the

long form (including permissions and owners) of the files in a directory

cat – an alternative to showing the data in a file all at once

pwd – display the current directorypasswd – change the password of the currently

logged in user

Remembering the basic Unix Commands

>> - append data to the END of a file> - overwrites the file and any data in it| - pipe character – strings commands together|| - logical OR – in that A || B in a loop, condition A or

condition B & - executes your process in the background – so you

can still use the command line ./script.sh & will run your process in the background

&& - Logical AND A && B if A succeeds, run Bsleep – stop execution of the script for a specified

number of seconds sleep 20 means sleep for 20 seconds

Manipulating data output

diff – compares two files (this is great for seeing what changes were made in a script against the original and modified)

sdiff – only works with the 132 character display, but compares files side by side

lp – prints a file to the configured printerlpstat – shows the user what is in the printer

queue( ) – runs the enclosed command in a sub-

shell(( )) – evaluates and assigns a value to a

variable and does math in a sub-shell

Manipulating data output

$(( )) – evaluates the enclosed expression[ ] – test an expression to see if it is true or

false< > - used to compare values or strings$( ) – command substitution – great when

doing logical OR’s or AND’s

Remembering the basic Unix Commands

++ - auto increment a value for I=1 ++ (takes I up by 1 for every loop)

-- - auto decrement a value for I=100 -- (takes I down by 1 for every loop)

<= - less than or equal to>= - greater than or equal to

Using math in a script

I will expect to see this in the header of every Unix Script you will turn in:

#!/bin/sh (tells the computer to use a bourne shell)## Script: Name of script (what you named this file)# Author: Your Name (so I know who wrote it)#Date: (the date you wrote it)#Revision: 1.1.A(how many times it changed, and what

state it is in(A, B, D, T or P) All scripts should also have A, B, D, T or P at the end of the

revision statement so I know if it is Alpha, Beta, Dev, Test, or Production. All scripts turned in should be production scripts

The header of every Unix Script

How to get your script to do more useful stuffIf. Thenif [test]

Thenstuff I want the computer to do

fiIf. Then. Else

if [test]Then

stuff I want the computer to doElse

Stuff I want the computer to do if the first condition didn’t happen

fi

Control Structures

forfor A=1

dostuff I want the computer to do

done

WhileWhile A=1

dostuff I want the computer to do

done

Control Structures

Until until A=1

dostuff I want the computer to do

done

Casecase A=1

stuff I want the computer to docase A != 1

stuff I want the computer to doeasc

Control Structures