[SOLVED] Or statement isn't working in script

digity · 02-09-2010, 02:22 PM

I'm trying to write a shell script with an OR statement and I believe the syntax is correct yet its not working properly - no matter what the value is it always response Yes! (even though the value is 09). Here's the script:

Code:

#!/bin/sh

DOM=`date +%d`

echo "Today's date of the month is the $DOM."

if [ $DOM="07" ] || [ $DOM="14" ] || [ $DOM="21" ] || [ $DOM="28" ]; then	
	echo "Yes!"	
else
	echo "No!"
fi

I've already tried using double equal signs (== instead of =), but I get the same results.

Any ideas?

digity · 02-09-2010, 02:41 PM

SOLVED! Apparently the spacing is very important. The needs to be a space surrounding the equal signs. This works:

Code:

#!/bin/sh

DOM=`date +%d`

echo "Today's date is the $DOM."

if [ $DOM = "07" ] || [ $DOM = "14" ] || [ $DOM = "21" ] || [ $DOM = "28" ]; then
	echo "Yes!"
else
	echo "No!"
fi

tredegar · 02-09-2010, 04:27 PM

Quote:

SOLVED!

Thanks for posting your solution. From your post #1:

Quote:

Any ideas?

You need to read man bash. But that's a PITA. man files are much easier to read when converted PDF's (especially as they are searchable).
You might like to see here
Have fun.

colucix · 02-09-2010, 04:36 PM

Quote:

Originally Posted by digity

Apparently the spacing is very important.

That's right. The question is why these expressions evaluated as TRUE. The answer is that they were interpreted as single and alone strings which are evaluated always as TRUE. E.g.

Code:

[ 09=07 ]     # this is TRUE
[ a ]         # this is TRUE as well

chrism01 · 02-09-2010, 04:39 PM

These are much easier to read than man pages (of any format)

http://rute.2038bug.com/index.html.gz
http://tldp.org/LDP/Bash-Beginners-G...tml/index.html
http://www.tldp.org/LDP/abs/html/

BTW http://www.tldp.org/LDP/abs/html/tes...ml#DBLBRACKETS

tredegar · 02-09-2010, 04:44 PM

Quote:

These are much easier to read than man pages (of any format)

Nice links. Bookmarked

chrism01 · 02-09-2010, 04:53 PM

Thx; my preferred version of man pages (and they are the definitive info for cmds) is http://linux.die.net/man/

digity · 02-09-2010, 07:05 PM

Quote:

Originally Posted by tredegar

You need to read man bash.

I'm confused - why do I need to read that?

pixellany · 02-09-2010, 09:11 PM

Quote:

Originally Posted by digity

I'm confused - why do I need to read that?

That gets you the built in manual (man) for bash. But some of the other links here are better.

Add one---at tldp, get the Bash Guide for Beginners