GNU Compiler Collection (GCC) and GNU C compiler (gcc)

• tools used to compile programs in Linux

Hello World! program compilation in C

• #include <stdio.h>

• int main()

• {

• printf("hello world!\n");

• }

PERL, Python, and bash—script interpreters in Linux

• Python is for rapid GUI development

• PERL is for complex jobs and Web pages

• bash is for everyday, general-purpose scripting.

Control structures used to develop scripting logic

• If...Then...Else statements

• Case statements

• For loops

• While loops

• table on page 907

BASH Scripting

• Shell scripting provides a way to automate everyday tasks into much simpler commands.

– For example, to add 200 users would require running the useradd command 200 times.

• The first line of a script identifies the shell or interpreter used to run this script.

– Linux uses BASH as the default shell so #! /bin/bash is the first line of BASH scripts.

• Any line with a # sign is a comment line. – Use comments to document what a

script is doing.

• BASH scripting is basically taking several commands into one file in the sequence you wish them executed.

• The read statement reads the value of a variable from stdin (standard input).

– It fetches input from the keyboard or a source redirected to it.

• read a will read a single value from stdin• read a b c will read multiple values on a single

line from stdin.

• You don’t have to declare variables, just use them

– VAR1 = 2– VAR2 = “Hello, World”

•

• Any arguments to the script are numbered $1, $2, $3, etc and used in the script by their numbers

• The echo line displays values. – It can display text: echo “Hello,

world”– It can display the contents of a variable:

echo VAR1

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Lab5.2

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Lab 5.4 pg919 ex.

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Lab 5.5

The Read command

• the Read command will be used with the While loop to take input from a file. This requires the use of the standard input redirector.

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