Re: Comparing files in two directories

[bob@proulx.com (Bob Proulx)]

L.V.Gandhi wrote:
> William Pursell wrote:
> > Here's a scriptlet that will print the name of all the files for
> > which diff produces more than 5 lines of output.  (Which is not quite
> > to say that they differ in 5 lines, but it's close).
> >
> > for file in $(find A -type f); do if test $(diff $file B/${file/A/} | wc -l) -gt 5; then echo $file; fi; done
> >
> 
> Can you please explain both $ part?

$(SOME COMMAND HERE) is "command substitution".  The "SOME COMMAND
HERE" part is executed and the output replaces the $(...) part.  The
first part runs 'find A -type f' as a command and the output is placed
there for the for loop to process.

Setup:

  mkdir t
  cd t
  touch a b c

This:

  for file in $(find . -type f); do

That is the same as:

  for file in ./a ./b ./c; do

Same thing for the $(diff ...) part.  The output replaces the $(...) part.

The $file part is variable expansion.  First it will be set to the
first thing, in my example "./a" and then the next, "./b" and so forth
through all of the strings in the for loop.

Bob