'check_framemd5.sh' Bash script for review

- It's more or less the situation... on February.
- I changed GREEN to BLUE, in order to make the script suitable for users suffering red-green colour blindness.

check_framemd5.sh

@@ -0,0 +1,86 @@
+#!/bin/bash
+  SCRIPT=$(basename $0)
+ VERSION='2016-07-10'
+  AUTHOR='Kieran O\'Leary, Reto Kromer'
+     RED='\033[1;31m'
+   BLUE='\033[1;34m'
+      NC='\033[0m'
+
+output_prompt() {
+    cat <<END_OF_MSG
+Usage: $SCRIPT [-h | <av_file> <md5_file>]
+END_OF_MSG
+}
+
+output_version() {
+    cat <<END_OF_MSG
+$SCRIPT $VERSION $AUTHOR
+END_OF_MSG
+}
+
+output_help() {
+    cat <<END_OF_MSG
+Syntax:
+  $SCRIPT
+    Prompts a short help message.
+  $SCRIPT -h
+    This help.
+  $SCRIPT <av_file> <md5_file>
+    Pass to the script the audio-visual file and the corresponding MD5
+    file to check.
+Dependency:
+  ffmpeg
+END_OF_MSG
+}
+
+if [ ! $(which diff) ] ; then
+    echo -e "${RED}ERROR:${NC} diff is not installed by default. Please install diffutils from Cygwin."
+    exit 1
+fi
+
+if [ "$#" -eq 0 ]; then
+    output_prompt
+    exit 0
+elif [ "$#" -eq 1 ]; then
+    if [ "$1" == '-h' ]; then
+        output_help
+        exit 0
+    elif [ "$1" == '-v' ]; then
+        output_version    
+        exit 0
+    else
+        echo -e "${RED}ERROR:${NC} '$1' is an invalid argument."
+        output_prompt
+        exit 1
+    fi
+elif [ "$#" -eq 2 ]; then
+    if ! [ -f "$1" ]; then
+        echo -e "${RED}ERROR:${NC} There is no file '$(basename $1)'."
+        output_prompt
+        exit 1
+    elif ! [ -f "$2" ]; then
+        echo -e "${RED}ERROR:${NC} There is no file '$(basename $2)'."
+        output_prompt
+        exit 1
+    else
+        if [[ $OSTYPE == "cygwin" ]]; then
+            md5_tmp=""$USERPROFILE/$(basename $2).tmp""
+        else 
+            md5_tmp="$HOME/$(basename $2).tmp"
+        fi
+        $(ffmpeg -y -i $1 -loglevel 0 -f framemd5 -an $md5_tmp)
+        old_file=$(grep -v '^#' $2)
+        tmp_file=$(grep -v '^#' $md5_tmp)
+        if [ "$old_file" = "$tmp_file" ]; then
+            echo -e "${BLUE}OK${NC} '$(basename $1)' matches '$(basename $2)'."
+        else
+            echo -e "${RED}ERROR:${NC} The following differences were detected between '$(basename $1)' and '$(basename $2)':"
+            diff "$2" "$md5_tmp"
+        fi
+        rm "$md5_tmp"
+    fi
+else
+    echo -e "${RED}ERROR:${NC} Too many arguments."
+    output_prompt
+    exit 1
+fi