bash: if santax help: [ X ] && [ Y ] || [ Z ]

**pqwoerituytrueiwoq** · April 29th, 2013

How do i write this in sh/bash

Javascript/php:

Code:

if ( 1 == 1 && ( 1==2 || 2==2 ) ) {

}

This is the closest i can get without breaking it:

Code:

if [ 1 -eq 1 ] && [ 1 -eq 2 ] || [ 2 -eq 2 ];then

fi

**varunendra** · April 29th, 2013

Edit: Forget it, it's all wrong. The following posts explain why.. trying variations, may post corrected one later..

Code:

if [[ 1 -eq 1 && 1 -eq 2 || 2 -eq 2 ]];then fi

works for me.

For example :

Code:

a=2; b=3; c=4; if [[ $a -eq 2 && $b -eq 2 || $c -eq 4 ]]; then echo yes; fi

..change the declared values or test values and see the difference. It works as -
IF (condition 1) AND (condition2 OR condition3), THEN go ahead..

**schragge** · April 29th, 2013

There's a subtle difference between &&/|| and -a/-o in that the former short-curcuit, but the latter don't. See compound comparison in ABS.

In this particular case, I'd use arithmetic evaluation

Code:

((1==1 && 1==2 || 2==2))

Also, using of parentheses to explicitly group subexpressions is allowed inside double-brackets and arithmetic expressions.

Edit || has lower precedence than &&, so parentheses are needed. See spjackson's explanation below.

**spjackson** · April 29th, 2013

The truth table for the original Javascript/php is:

Code:

TTT==>T
TTF==>T
TFT==>T
TFF==>F
FTT==>F
FTF==>F
FFT==>F
FFF==>F

However both of these suggestions:

Code:

if [[ 1 -eq 1 && 1 -eq 2 || 2 -eq 2 ]];then

((1==1 && 1==2 || 2==2))

have the truth table

Code:

TTT==>T
TTF==>T
TFT==>T
TFF==>F
FTT==>T
FTF==>F
FFT==>T
FFF==>F

i.e. different in 2 cases.

Just as in the original, you need a bracket;

Code:

if [[ 1 -eq 1 && ( 1 -eq 2 || 2 -eq 2 ) ]];then

((1==1 && (1==2 || 2==2)))

**varunendra** · April 29th, 2013

Originally Posted by spjackson

Just as in the original, you need a bracket;

Code:

if [[ 1 -eq 1 && ( 1 -eq 2 || 2 -eq 2 ) ]];then

Verified this one ^^ with my example, changing all three variables and seems perfect!

**pqwoerituytrueiwoq** · April 29th, 2013

Thanks everyone

this is where i needed it

**schragge** · April 29th, 2013

Two things about your script.

1. It downloads kernel-related packages to current directory and then counts files to check if they were successfully downloaded. What if there already were previously downloaded older kernel packages in the folder?

2. This

Code:

if [ "`uname -m`" == "x86_64" ];then
arch="amd64"
else
arch="i386"
fi

probably could be replaced with

Code:

arch=`dpkg --print-architecture`

and this

Code:

[ $(ls /boot | grep $VER_A | wc -l) -gt 3 ]

with

Code:

[[ -d /lib/modules/$VER_A ]]

**pqwoerituytrueiwoq** · April 29th, 2013

If there are files present it will ask you if you want to delete them, if you say no wget will not replace them and will get the other files
edit:
opps now what you meant, thanks

https://github.com/GM-Script-Writer-...criptGenerator