Bourne Shell to CShell

Question

This works fine:

#!/bin/sh

ALTER="$1"
NAME="$2"

for pr in $(pgrep $NAME); do
    elapse=$(ps -o etime= -p $pr)
    [ "${elapse%:*}" -gt "$ALTER" ] && echo $pr
done

But if I try to switch it to CShell:

#!/bin/csh

set ALTER = "$1"
set NAME = "$2"

for pr in $(pgrep $NAME); do
    set elapse = $(ps -o etime= -p $pr)
    [ "${elapse%:*}" -gt "$ALTER" ] && echo $pr
done

I get an Illegal variable error. Any ideas?

Answer 1

The first thing you should know about scripting in csh is that it is usually a very bad idea. That said, if you insist, the problems with your script are:

• csh doesn't support the $() construct for command substitution, use ` ` instead.
• csh doesn't support the for i ... do ... done syntax, use foreach i ... end instead.
• csh doesn't do funky string manipulation like "${elapse%:*}". You'll have to get around it using some other tool.
• I don't know how to get [ to work with csh (but it's probably possible), as a workaround, use if instead.

So, a working version of your script in csh would be:

#!/bin/csh
set ALTER = "$1" 
set NAME = "$2" 
foreach pr  (`pgrep "$NAME"`)
    set elapse = `ps -o etime= -p "$pr" | cut -d: -f1` 
    if ( "$elapse" > "$ALTER" ) echo "$pr"
end

Seriously though, don't script in csh, it will only cause you pain. Especially since all you really need is:

 ps -o pid=,etime= -p $(pgrep $NAME) | cut -d: -f1 | 
        awk -vval="$ALTER" '$2>val{print $1}'

Answer 2

${var%$pattern} is a POSIX-shell construct (introduced by ksh) not available in csh.

You could use expr here:

expr "$elapse" : '\([0-9]*\)' '>' "$ALTER" > /dev/null && echo $pr

But I would first

1. avoid csh
2. avoid csh
3. avoid loops in shell scripting. Here the whole thing can be done by piping ps to awk in a syntax compatible with most shells.