First: the "backquotes" should not be used any more. They are only there for compatibility issues but their usage is strongly discouraged. instead of `command` use

Code:

$(command)

.

Second: command substitution. Suppose you run a command "somecommand" and it produces some output - any output.

Code:

user@host:/some/where> somecommand
this is some output

You can use this output inside your own commands by using the command substitution device ("$( .... )"). The shell will first run the denoted command, replace the command substitution with its output and only then execute the rest of the line. In the example above, consider:

Code:

user@host:/some/where> echo "== $(somecommand) =="

The first step is to run "somecommand" and replace it with its output:

Code:

echo "== this is some output =="

Then, the resulting command is executed, simply displaying the original output decorated with surrounding equal-signs.

This example is not doing something impressive, but in fpmurphy's case it dealt with a possibly varying command output. This line:

Code:

if (( $(stat -c %s file1) >  $(stat -c %s file2) ))

boils down to:

Code:

if (( 5 > 4 ))

or something such, depending on what "stat -c %s <filename>" would yield.

Btw.: you might notice a slight flaw in your programs logic. What would happen if the two files are of absolutely equal size? The solution is left to the reader, but a hint may be in order: "if"-statements can be nested.

I hope this helps.

bakunin