difference between echo and ""

Shell Programming and Scripting
1

hi guys
wht is the difference between these two command in bash shell scripting
$var1=world!
$echo hello $var1
$echo "hello $var1"

2 
$ var1='World!'
$ echo Hello $var1
Hello World!
$ echo Hello  $var1
Hello World!
$ echo "Hello $var1"
Hello World!
$ echo "Hello  $var1"
Hello  World!
$

The quotes tell the shell to interpret Hello and the substitution of var1 as one parameter (including the space(s)), instead of two parameters.

3

thanks for reply
i am little bit confused...
can u tell me clearly.....
plzzzzz

4

The shell uses the space character ' ' as seperator for arguments passed to commands.
The line

echo Hello World

is parsed by the shell like this:

  • Command: echo
  • First argument: Hello
  • Second argument: World

The line

echo "Hello World"

is parsed by the shell like this:

  • Command: echo
  • First argument: Hello World
5

vow great...
now i understood ....very clearly
thank you ...thank you very much....

6

In addition to what has been already posted, the version in quotes will preserve multiple space characters.
Try with say three spaces between "hello" and "world":

echo "hello   world"
hello   world


echo hello   world
hello world
7

Actually both " " and ' ' turns off the special meanings of the meta characters, except that " " doesn't do that for \ $ ' and ".

But from the number of arguments interpretation point of view, at least in KornShell they function the same way.

#!/bin/ksh

VALUE1="hello world"
VALUE2='hello world'

for ITERATOR in $VALUE1
do
    print "$ITERATOR"
done

for ITERATOR in $VALUE2
do
    print "$ITERATOR"
done

Both of them will print

hello
world

In each loop there is two arguments (two values for $ITERATOR)

8

But as soon as you change the loop to

for ITERATOR in "$VALUE1"

it's only one iteration again

9

Yes, you're right, I didn't know that, thanks for this remark :smiley: