As a part of my tcl script, my requirement is i need to delete
contents (i.e. files and directories with my login id) from remote
machine. So i am using following code

catch {exec  /usr/bin/rsh $mac_n {\rm -r ls -lrt /local/test | grep
$username | awk {{ print $NF}}}} err1

Now this code deletes files successfully and instantaneously but it
hangs while deleting folders.

I also tried an alternative solution for deleting files of my login
using csh script, but again while executing same script from tcl it
hangs.

It would also help if you described exactly what results (independent
of the side-effect of deleting stuff) you expect to get out of it.

exec ls -ltr | grep userid | awk {{print $NF}} | xargs rm -r

Now this code is working only on running this on that particular
machine. If i want to run this code from a remote machine, this is
still not working.

I have lot of machines (linux, solaris and ibm machines) where i need
to perform this operation as i can't do this operation manually. I
want to do this operation form tcl script only.

Now for deleting data from remote machine, i am using following code:

exec /usr/bin/rsh machine_name "(cd /local/test; ls -ltr | grep
$userid | awk {{print $NF}} | xargs rm -rx}"

Now this is reporting error : undefined variable NF.

So if i do it like :

exec /usr/bin/rsh machine_name {(cd /local/test; ls -ltr | grep
$userid | awk {{print $NF}} | xargs rm -rx}}

Then it is reporting error as : Missing }

  exec /usr/bin/rsh $host "find /local/test -user $userid -delete"

I'm putting the string to execute remotely in double-quotes because I
want the user id to be substituted _locally_ and I'm assuming it has
no evil characters in it (that's a pretty safe assumption for user
names!)

Note: it doesn't need ls, or grep, or awk. (It could have been written
with xargs, but there's good reasons to not do that when deleting
directory hierarchies.)

    exec /usr/bin/rsh $host "find /local/test -user $userid -exec rm \\
{\\} \\;"

The backslashes are doubled for Tcl substitution (passing them as
singles), and then the resulting \{\} and \; are two shell-escaped
arguments to 'find'.

Finally it worked with:

exec /usr/bin/rsh $host "cd /local/test; find . -user $userid -exec rm
\\{\\} \\;"

Now one question still remains, why this was not working with the
following code:

exec /usr/bin/rsh machine_name "(cd /local/test; ls -ltr | grep
$userid | awk {{print $NF}} | xargs rm -rx}"

I have read some where on net that for awk to work with tcl, you
should use '{' instead of '. Now if i execute same code by logging
into machine manually from tcl shell, it works absolutely fine.

exec ls -ltr | grep userid | awk {{print $NF}} | xargs rm -r

To resolve this , i had used

exec /usr/bin/rsh machine_name {(cd /local/test; ls -ltr | grep
$userid | awk {{print $NF}} | xargs rm -rx}}

But it was not substituting variables, and hence was getting error.

Any idea on how to make it work through awk code as well.

Indeed, in  the above, "(cd /local/test; ls -ltr | grep $userid | awk
{{print $NF}} | xargs rm -rx}" is a single string passed as the 3rd
argument to [exec].
Following Tcl's rules with double quotes, normal dollar+backslash
+bracket expansion occurs. You do want it to dollar-expand $userid,
but you don't for $NF (because you want awk to see the dollar). That's
error (1), fix it by saying \$NF.

Then, none of the braces receives any special attention from Tcl's
toplevel-double-quotes processing, so they go through untouched, down
to the shell (spawned by rsh remotely), to which a curly brace has a
completely unwanted meaning. That's error (2), fixed by using single
quotes.

So the final fixed code should be:

   exec /usr/bin/rsh machine_name "(cd /local/test; ls -ltr | grep
$userid | awk '{print \$NF}' | xargs rm -rx}"

    exec awk {{print $1}}
    exec sh -c {awk '{print $1}'}
    exec sh -c "awk  '{print \$1}'"
    exec sh -c {awk "{print \$1}"}

all end up printing column 1. Look at them in detail to understand
why. After that you'll never hesitate again :)

Note that there still is a paren mismatch (the remote command starts
with "(" and ends with "}") -- most probably a left-over from previous
try-and-error by the OP...

To the OP: so the final fixed code should be:

      exec /usr/bin/rsh machine_name "cd /local/test; ls -ltr | grep
$userid | awk '{print \$NF}' | xargs rm -rx"