Running a diff on all pairs of arguments

Shell Programming and Scripting
1

I would like to create a loop and an inner loop to do a diff command on each pair of files passed as arguments. For example, if four files were on the command line, a diff would run on 1-2, 1-3, 1-4, 2-3, 2-4, & 3-4. Thus far I know the $# will give the count of the arguments and argv (instead of shift) would be used to refer to each argument, but I don't know how to define or modify variables which would be used as subscripts.

TIA

2

What operating system and shell are you using?

Most of us avoid csh when writing scripts, but your reference to argv doesn't sound like you are using a shell based on Bourne shell syntax.

3

Use two nested for loops, the outer running var_i from 1 to $#-1, the inner running var_j from var_i+1 to $#. You then need eval to run the diff command inside the loops:

eval diff \$$var_i \$$var_j
4

It's SCO Unix and I believe it uses the Bourne Shell.

5

If it doesn't have a Bourne shell it's not UNIX.

I don't think you need eval for this:

FIRST="$1"
shift

IFS="^" # Needs to be some char not present in your input
REST="$*"

while [ ! -z "$REST" ]
do
        while [ "$#" -ne - 0 ]
        do
                echo diff "$FIRST" "$1"
                shift
        done

        set -- $REST
        FIRST="$1"
        shift
        REST="$*"
done