Make colours, escape sequences optional

Coloured output is tedious to parse, even unnecessary where the report
backend is not a terminal.

Signed-off-by: lusitania <lusitania@users.noreply.github.com>

README.md

@@ -51,4 +51,10 @@ cd docker-bench-security
 sh docker-bench-security.sh
 ```
 
+Coloured output may be switched off to ease parsing:
+
+```sh
+sh docker-bench-security.sh -n |& grep '^\[WARN\]'
+```
+
 This script was build to be POSIX 2004 compliant, so it should be portable across any Unix platform.

docker-bench-security.sh

@@ -37,6 +37,7 @@ usage () {
   cat <<EOF
   usage: ${myname} [options]
 
+  -n           optional  Don't colourise results
   -h           optional  Print this help message
   -l PATH      optional  Log output in PATH
 EOF

output_lib.sh

@@ -1,9 +1,21 @@
 #!/bin/sh
+getopts n opts
+case "$opts" in
+    n)
+        bldred=
+        bldgrn=
+        bldblu=
+        bldylw=
+        txtrst=
+        ;;
+    *)
         bldred='\033[1;31m'
         bldgrn='\033[1;32m'
         bldblu='\033[1;34m'
         bldylw='\033[1;33m' # Yellow
         txtrst='\033[0m'
+        ;;
+esac
 
 logit () {
   printf "%b\n" "$1" | tee -a "$logger"