Just wondering why I can execute the following fine in bash:
echo "first second third" | awk '{ print $1 }'

But if I have the following in my TCL script it just won't work:
[echo "first second third" | awk '{ print $1 }']

Following site said that it's because bash will strip off the ' before passing to awk and recommends awk {{ print $1 }}. However this never return anything in my TCL. Any idea?
http://phaseit.net/claird/comp.lang.tcl/fmm.html

All I want is to be able to extract a specified column from a line of text within TCL. If anyone can provide any tips that'd be much appreciated!

er, well,
it's because that is not TCL.
you've just put a bash line in [].

for a start its puts in TCL not echo.

have you not read the tcl website?

you would use split
you need to do a tutorial to get the basics.

Okay thanks I'll give that a try. However, that link I referenced does use echo instead of put. I've even tried putting it like this but it doesn't work.
exec echo "col1 col2 col3" | awk {{ print $1 }}

It is way off to call that Bash statement from TCL. Like Bigearsbilly said, you should use the split statement.

If you have good reasons to call a Bash string from TCL, this won't work. First you need to use the eval command to get the paramters passed to Bash, secondly piping probably won't work as the pipe is seen as an additional parameter.

What is your reason to refer to TCL anyway?

jlinkels

actually split isn't enough as it splits on each space in tcl, not a regex,
unlike shell or perl.
so you'll get empty fields for multiple spaces.
a bit annoying.

Hello,

Just wondering how come I can do these from within TCL (exactly the same as I would type in the bash prompt):
exec /sybase/ase12.5/OCS-12_5/bin/isql -Uuser -S Ftest -P user123 -i $queryFile -o $recordSetFile -w 800
exec chmod 755 $file

But not this:
exec echo "col1 col2 col3"

It appears that for the first one, TCL took whatever is after the "exec" keyword and execute them in the normal shell. However, this certainly isn't the case which explains why the second one didn't work. However, I'm not able to determine why. Any ideas?

I've also see the following works:
[procName argName]

And simply procName argName without the brackets. So when should I use bracket and when shouldn't I?

Can someone point me to an example of eval?

Also the following works:
puts {echo col1 col2 col3 | awk {{ print $1 }}}

However, all that it is doing is to print the statement without executing it.

Have you read the eval command?

jlinkels

I know. I once used a two-stop process for that by first regsub to convert all spaces into single spaces or one single other character, and then apply split

It is extremely annoying, especially if you parse a string and have a {} unexpectedly while you were retrieving a value using lindex. Very catastrofal program crashes result.

jlinkels

Guys, never mind the questions. I got it working using:
set item [lindex $var 0]

I now have another problem with regexp which I'd make a new thread instead.