Identify how similar a file is to each file in a group of others.

similarities.sh

#!/bin/bash

fileA="$1"
shift
for fileB in "$@"; do
    (
        # diff once grep twice with the help of tee and stderr
        diff $fileA $fileB | \
            tee >(grep -cE '^< ' >&2) | \
                  grep -cE '^> ' >&2
    # recapture stderr
    ) 2>&1 | (
        read -d '' diffA diffB;
        printf "The files %s and %s have %s:%s diffs out of %s:%s lines.\n" \
            $fileA $fileB $diffA $diffB $(wc -l < $fileA) $(wc -l < $fileB)
    )
done | column -t

$ similarities.sh terraform.tfvars ../*/terraform.tfvars
The  files  terraform.tfvars  and  ../api_proxy/terraform.tfvars                   have  3:3   diffs  out  of  51:51  lines.
The  files  terraform.tfvars  and  ../cf-ip-location-lookup/terraform.tfvars       have  4:12  diffs  out  of  51:59  lines.
The  files  terraform.tfvars  and  ../cf-region-cookie-setter/terraform.tfvars     have  4:8   diffs  out  of  51:55  lines.
The  files  terraform.tfvars  and  ../cf-switch-region-origin/terraform.tfvars     have  4:10  diffs  out  of  51:57  lines.
The  files  terraform.tfvars  and  ../reformat_devops_alerts/terraform.tfvars      have  0:0   diffs  out  of  51:51  lines.
The  files  terraform.tfvars  and  ../restart_location/terraform.tfvars            have  17:3  diffs  out  of  51:37  lines.
The  files  terraform.tfvars  and  ../warehouse-availability-etl/terraform.tfvars  have  3:3   diffs  out  of  51:51  lines.