Newbie script question...

[Gene Laoyan]

OK, in VB there is an "If" statement that checks two variables then take action like so...
If var1="Dead" And var2="Live" then

'Do something...

ElseIf var1="Live" And var2="Dead" then

'Do something...

End If

How can I do that in a POSIX script?

[john korterman · Accepted solution]

Hi Gene,

you can try something like this:

$ cat decide.sh
#!/usr/bin/sh

if [[ ${1} = "Dead" && ${2} = "Alive" ]]
then
echo "${1} is Dead and ${2} is Alive"
elif [[ ${2} = "Dead" && ${1} = "Alive" ]]
then
echo "${1} is Alive and ${2} is Dead"
else
echo " neither nor..."
fi

And execute with two parameters, e.g.:
$ ./decide.sh Dead Alive

regards,
John K.

[Peter Nikitka]

Hi,

another possibility would be a 'case' statement, which is easier to read, IMHO:

check="$var1"-"$var2" # use appropriate delimiter

Such use easily can check e.g. if 'at least one is alive':
case $check in
*Live*) echo Yeah ;;
esac

A complete check:
case $check in
Dead-Live) echo 1st;;
Live-Dead) echo 2nd ;;
Live-Live) echo both ;;
Dead-Dead) echo none ;;
esac

mfG Peter

[James R. Ferguson]

Hi Gene:

In the shell, '-a' represents 'and' and '-o' signifies 'or'. Parenthesis used for logical grouping need to be escaped. The '!' operator denotes negation. The '&&' and '||' are often used to create compound expressions.

Have a look at the manpages for 'test' and for 'sh-posix'.

http://www.docs.hp.com/en/B2355-60127/test.1.html

http://www.docs.hp.com/en/B2355-60127/sh-posix.1.html

Consider:

# cat testit
#!/usr/bin/sh
if [ \( "$1" = "dead" -o "$1" = "expired" \) -a "$2" != "alive" ]; then
echo "it's very dead!"
fi

[ \( "$1" = "dead" -o "$1" = "expired" \) -a "$2" != "alive" ] && echo "dead!";

exit 0

# ./testit expired unsure
it's very dead!
dead!

Regards!

...JRF...

[Gene Laoyan]

All great answers and all worked. I used the example that john korterman gave because it was closer to what my simple mind can understand.

Thanks everyone!