created paramater parsing

- UNIX style (incl. clustered) parameter parsing
    - help prompt `-h`
    - suffix mode `-b | -o`
    - destination `-d DIR`
    - multiple file names gathered in array
- help prompt up-to-date

.gitignore

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+/test-env

bak-old.sh

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+#!/bin/bash
+
+###################################
+# authored by github.com/kevinnls #
+#   - another Linux user tired of #
+#     type cp file file.bak       #
+###################################
+
+### IFS precautions
+OLDIFS="$IFS"
+unset IFS
+
+### parse parameters
+# file names
+# `-d` dest dir
+# `-b | -o` mode: cloned file suffix
+# ` ` follow symlinks
+# ` ` lightweight copies
+
+print_usage(){
+cat << HERE
+$(tput bold; tput setaf 3)${0##*/}$(tput sgr0)
+    Create copies of files with .bak or .old suffixes
+$(tput bold)USAGE$(tput sgr0)
+    $(tput bold)${0##*/}$(tput sgr0) [-b|o] FILES [ -d DESTINATION ]
+
+$(tput bold)OPTIONS$(tput sgr0)
+  Suffix for FILES -- only one can be used
+    -b	$(tput bold).bak$(tput sgr0) [default]
+    -o	$(tput bold).old$(tput sgr0)
+  Destination for clones
+    -d	\`cp FILES DESTINATION/FILES.suffix\`
+HERE
+}
+
+set_dest(){
+    dest=$1
+}
+set_mode(){
+    if [[ -z $mode ]]; then
+	mode=$1
+    else
+	inexclusive_flags
+    fi
+}
+add_file(){
+    files=("${files[@]}" "$1")
+}
+
+parse_combined(){
+
+    combi=${1/-/}
+
+    in_combi(){
+	[[ "$combi" =~ [:alnum:]*($1){1}[:alnum:]* ]]
+    }
+    un_combi(){
+	combi=${combi/$1/}
+    }
+
+    if in_combi 'b';then
+       set_mode bak
+       un_combi 'b'
+    fi
+    if in_combi 'o'; then
+       set_mode old
+       un_combi 'o'
+    fi
+
+    [[ "$combi" =~ [:alnum:]*(d){1} ]] && set_dest $2 && ret=2
+
+    if [[ -z "$combi" ]]; then
+	return ${ret:-1} #return number of positions to shift
+    else
+	tput setaf 1
+	echo "ERROR: unrecognised flags"
+	tput sgr0
+	print_usage
+	exit 1
+    fi
+}
+
+inexclusive_flags(){
+    echo "modes backup and old cannot co-exist"
+    exit
+}
+
+while [[ $# -gt 0 ]]; do
+    case $1 in
+	'-h' )
+	    print_usage
+	    exit 0
+	    ;;
+	'-d' )
+	    set_dest "$2"
+	    shift 2
+	    ;;
+	'-b' )
+	    set_mode bak
+	    shift 1
+	    ;;
+	'-o' )
+	    set_mode old
+	    shift 1
+	    ;;
+	-* )
+	    parse_combined "$1" "$2"
+	    shift $?
+	    ;;
+	* )
+	    add_file "$1"
+	    shift 1
+	    ;;
+    esac
+done
+
+echo params sanitised
+echo files: ${files[@]}
+echo mode: $mode
+echo dest: $dest
+
+### reset IFS
+IFS="$OLDIFS"