if ! not working in ksh

[dictum9]

This is 11.0, N class machine.

I can get the following to work on the command line if I type it in, but not in a script. In a script, it complains about the "!".
The script starts with #!/bin/ksh.
Why is that, is there a bug?


if ! grep "Synchronizing" $STATE
then
echo not
else
echo yes
fi

[Tim Nelson · Accepted solution]

most likely need some quoting...

other option

if grep "Syncronizing" $STATE
then
echo yes
else
echo no
fi

[Tim Nelson]

Now that I think more..

I do not think you can use "if !"

typically you would either "if true" or "if false". Not "if not true."

[James R. Ferguson]

Hi:

This should be:

if [ `grep -c "Synchronizing" $STATE` -eq 0 ]
...

That is, it appears that you want to test whether or not there are any occurances of "Synchronizing" in the (file) ${STATE}.

Another way is to examine the return value of grep (zero meaning that there *is* a match):

# grep "Synchronizing" ${STATE} && echo "yes" || echo "no"

Regards!

...JRF...

[James R. Ferguson]

Hi (again):

Ooops. The last suggestion is best done with the '-q'uiet switch (since you don't want the output; only the success or failure of the match:

# grep -q Synchronizing ${STATE} && echo yes || echo no

Regards!

...JRF...

[Dennis Handly]

>Tim: I do not think you can use "if !"

Right, it is only available in [ ] or conditional expressions in [[ ]].
Or !(pattern-list).
And of course in arithmetic expressions in (( )) or let.

[Peter Nikitka]

Hi,

this feature is not available in the standard ksh; in the ksh93 version, it is.
So if you want to try, use
/usr/dt/bin/dtksh
as the shell for your script.

mfG Peter

[dictum9]

I ended up not using "!" and reversing the if statement.

Still not real clear as to why it works in shell but not in the script.

[OldSchool]

"Still not real clear as to why it works in shell but not in the script...."

well, it would appear that the shell you work in is not ksh.

easy test, type in /bin/ksh and then enter the command. does it work?

[Daavid Turnbull]

It is shell specific so it may depend on what you have as your #! line at the top which I suspect points at a different shell.

"man test" is your friend for this sort of stuff.

I tend to be a bit old school and tend to do something like:

grep -q "some string" "some file"
if [ $? -ne 0 ]
then
echo "some string not found"
fi


Because to me it makes it clear that it is the exit code that is being Analyzed in the conditional.

[Dennis Handly]

>Peter: this feature is not available in the standard ksh

You're right, it is highlighted on my sh-posix(1) entry. ;-)

>OldSchool: it would appear that the shell you work in is not ksh.

Most likely, sh.

>Still not real clear ... but not in the script.

Change to: #!/bin/sh.

>Daavid: "man test" is your friend for this sort of stuff.

Not if you are using ksh or the posix shell.  And test(1) is only for stuff in [...].

And more importantly, test(1) just invokes the posix shell.

[James R. Ferguson]

Hi (again):

> Dennis wrote :Change to: #!/bin/sh.

To be clear, '/bin' is a link to '/usr/bin'. '/usr/bin/sh' is the POSIX shell in HP-UX. The Korn-88 shell is represented by '/usr/bin/ksh' and the Korn-93 shell can be found as '/usr/dt/bin/dtksh'. The (useless?) Bourne shell can be found as '/usr/old/bin/sh'.

Regards!

...JRF...