diff variables within a script

Question

I realize that the diff command is reserved for directories/files, but I've seen it being able to read from standard input, so that's not necessarily true.

Is it possible to somehow compare two variables that were stored in a ksh script?

The code looks like this:

a=$(cut -c 1-10 first_file.txt)
b=$(cut -f '3' -d ' ' second_file.txt)

#what I would like to do
$(diff $a $b) > differences.txt

mfinni · Answer 1 · 2011-01-06T21:18:15.573

1

Use process substution (thanks, Dennis!) as described here. This would probably do it

diff <(echo $a) <(echo $b)

At least, that worked for me in bash on cygwin.

edited Jan 06 '11 at 21:18

answered Jan 06 '11 at 20:33

mfinni

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That's process substitution rather than input redirection. – Dennis Williamson Jan 06 '11 at 21:14
Well, with the <, it's both, right? – mfinni Jan 06 '11 at 21:16
Nope, I'm wrong, you're right. – mfinni Jan 06 '11 at 21:17
Sorry, `ksh` doesn't like it. – Nitrodist Jan 06 '11 at 21:32
So figure out the syntax for process substitution on ksh. – mfinni Jan 06 '11 at 21:34
Looks like it might be ($(...) from what Wikipedia tells me, so try : diff <($(echo $a)) <($(echo $b)) – mfinni Jan 06 '11 at 21:39

diff variables within a script

1 Answers1