how to use "!" and "diff" command ?

[Manuales]

Hi ..
how can i to use "!" with diff for the following command:


if ! diff $environment/vgp_$(hostname).txt ${LOG}/${A}_vgp.TEMP > ${LOG}/${A}_vgp.DIFFERENT

if i run above sentence, the result is:
01_bdf_filesystem.sh[40]: !: not found

for avoiding "else" ... i need to know it when it is different ...

Please let me know.

[James R. Ferguson · Accepted solution]

Hi Manuales:

That's not legal Posix/KSH syntax. I suggest something like this:

# diff $environment/vgp_$(hostname).txt ${LOG}/${A}_vgp.TEMP > ${LOG}/${A}_vgp.DIFFERENT
# RETURN=$?
# if [ "${RETURN}" != 0 ]; then
> echo different
> else
> echo no_different
> fi

Regards!

...JRF...

[Manuales]

It worked ... thanks a lot !!!!!
:0)

[Raj D.]

Manuals,

You can use it like this to see the difference between the two :

#########################################
diff $environment/vgp_$(hostname).txt ${LOG}/${A}_vgp.TEMP > ${LOG}/${A}_vgp.DIFFERENT

if [ -s ${LOG}/${A}_vgp.DIFFERENT ]
then
echo "Difference Found "
echo "" ; echo "Difference is : "
cat ${LOG}/${A}_vgp.DIFFERENT

else
echo "No Difference found! "
fi
##########################################


Cheers,
Raj.

[Dennis Handly]

>JRF: That's not legal Posix/KSH syntax.

Actually ! script is legal in sh. I found this out last time it was asked.

[Peter Nikitka]

Hi,

all Bourne-like shells allow this construct in using 'else':

if diff a b
then :
else
do_what_is-needed
fi

BTW, ksh93 (/usr/dt/bin/dtksh) permits the above 'if ! ' construct.


mfG Peter

[James R. Ferguson]

Hi Dennis & Peter:

Dennis > Actually ! script is legal in sh. I found this out last time it was asked.

...and so *I* have not learned, too. Thanks, Dennis * Peter.

Regards!

...JRF...