Discovering the concept of linux

Hello everyone ;

I am Teertha Darekar

Welcome back to my day 8 blog of linux Workshop conducted by :-Pranav Jambare sir.

CONTENTS :-

Loops

let's start ;

A loop is a powerful programming tool that enables you to execute a set of commands repeatedly.
There are three types of loops in linux .
1. While loop
2. Until Loop
3. For Loop

1 ) While Loop :-

If the condition remains satisfied the loops runs , if condition raise to false then loop will be terminated .

Syntax :-

while <condition>
do 
    statement executed if the command is true
done

Example :-

#!/bin/bash
A=0
while [ ${A} -lt 20 ];
do
    echo " ${A}"
    A=` expr ${A} + 1`
done

2) Until Loop :-

If the condition remains unsatisfied the loops runs , The loop terminates when the condition becomes true.

Syntax :-

until <condition>
do
    statement executed if the command is true
done

Example :-

#!/bin/bash
A=20
until [ ${A} - lt 00 ];
do
    echo " ${A}"
    A=` expr ${A} - 1`
done

3) For Loop :-

The for loop operate on lists of items. It repeats a set of commands for every item in a list.

Syntax :-

for var in word1 word2..wordn                  --(var=variable)
do
    statement executed till element end
done

Example :-

#!/bin/bash
for var in Teertha Swar Purva Prashant;
do
    echo " my name is ${var}"
done

To print the names from file :-

for name in $(cat/root/name)        *name = file name*                
do
    echo "current name is ${name}"
done

Command Line Argument :-

Command-line arguments are parameters that are passed to a script while executing them in the bash shell.

$1 $2 $3 -> Arguments passed .

$0 -> Name of the shell program .

$@ -> One by one arguments passed .

$# -> Total number of arguments .

$* -> All arguments together .

$$ -> PID(Process ID) of current shell. (Actually the program PID can be achieve) .

$? -> Status of last command .

$! -> PID of last command.

Thank youu ....

Linux Workshop :- day 8