file-eq

#!/bin/sh

##
# file-eq:
# return true iff two files are equal.
#
# Syntax:
#
#     file-eq <file1> <file2>
#
# Example:
#
#     $ file-eq foo.txt bar.txt
#
# How the script compares the files:
#
#   * Is each file a real file and not directory, symlink, etc.?
#   * Are the two files the same size, and do they have the same content?
#   * If the files are equal, then exit 0, else nonzero.
#
#
# ## Customization
#
# To calculate file size we try to use the `du` command, then try others.
#
# To do file comparisons, we use the `cmp` command.
#
# You can customize the commands by using environment variables:
#
#     DU=/foo/du CMP=/goo/cmp
#
#
# ## Tracking
#
#   * Program: file-eq
#   * Version: 2.0.0
#   * Created: 2014-12-02
#   * Updated: 2017-09-06
#   * License: GPL
#   * Contact: Joel Parker Henderson (joel@joelparkerhenderson.com)
##
set -euf

arg_file1="$1"
arg_file2="$2"

out () { printf %s\\n "$*" ; }

file_size() {
  file="$1"
  size=$(
    ${DU:-du}  --apparent-size --block-size=1 "$1" 2>/dev/null ||
    ${GDU:-gdu} --apparent-size --block-size=1 "$1" 2>/dev/null ||
    ${FIND:-find} "$1" -printf "%s" 2>/dev/null ||
    ${GFIND:-gfind} "$1" -printf "%s" 2>/dev/null ||
    ${STAT:-stat} --printf="%s" "$1" 2>/dev/null ||
    ${STAT:-stat} -f%z "$1" 2>/dev/null ||
    ${WC:-wc} -c <"$1" 2>/dev/null
  )
  q=$?; [ $q -eq 0 ] || exit $q
  out "$size" | awk '{print $1}'
}

file_eq() {
  file1="$1"; file2="$2"
  [ -f "$file1" ] && [ ! -L "$file1" ] &&
  [ -f "$file2" ] && [ ! -L "$file2" ] &&
  [ $(file_size "$file1") == $(file_size "$file2") ] &&
  ${CMP:-cmp} -s "$file1" "$file2"
  return
}

file_eq "$arg_file1" "$arg_file2"