Shell script arguments

Question

I just started writing shell scripts in Unix so, I am a total newbie

I want to read the arguments given when the user run the script ex:

sh script -a abc

I want to read for argument -a user gave abc.

My code so far:

if ( $1 = "-a" )
then var=$2
fi
echo $var

I get an error.

Use square brackets instead of parenthesis: if [ $1 = "-a" ] — devnull
– devnull, Commented May 9, 2014 at 11:10

fvu · Accepted Answer · 2014-05-09 11:10:37Z

3

Bash uses an external program called test to perform boolean tests, but that program is used mostly via its alias [.

if ( $1 = "-a" )

should become

if [ $1 = "-a" ]

if you use [ or

if test $1 = "-a"

answered May 9, 2014 at 11:10

fvu

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2 Comments

andrew Over a year ago

I had no idea that's what [] was actually doing +1

fvu Over a year ago

I think many people don't realize that [ is in fact an executable. Not sure and not able to test it right away, but Bash has an extended/enhanced/improved test, [[ which I think is built-in.

YaleCheung · Accepted Answer · 2014-05-09 11:40:09Z

1

#!/bin/sh

if [ $1 = "-a" ]; then
    var=$2
fi
echo $var

You shoud be careful of the space between if and [

answered May 9, 2014 at 11:40

YaleCheung

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