Data commit

Task/Caesar-cipher/UNIX-Shell/caesar-cipher.sh

@@ -0,0 +1,56 @@
+caesar() {
+    local OPTIND
+    local encrypt n=0
+    while getopts :edn: option; do
+        case $option in
+            e) encrypt=true ;;
+            d) encrypt=false ;;
+            n) n=$OPTARG ;;
+            :) echo "error: missing argument for -$OPTARG" >&2
+               return 1 ;;
+            ?) echo "error: unknown option -$OPTARG" >&2
+               return 1 ;;
+        esac
+    done
+    shift $((OPTIND-1))
+    if [[ -z $encrypt ]]; then
+        echo "error: specify one of -e or -d" >&2
+        return 1
+    fi
+
+    local upper=ABCDEFGHIJKLMNOPQRSTUVWXYZ
+    local lower=abcdefghijklmnopqrstuvwxyz
+    if $encrypt; then
+        tr "$upper$lower" "${upper:n}${upper:0:n}${lower:n}${lower:0:n}" <<< "$1"
+    else
+        tr "${upper:n}${upper:0:n}${lower:n}${lower:0:n}" "$upper$lower" <<< "$1"
+    fi
+}
+
+tr() {
+    local -A charmap
+    local i trans line char
+    for ((i=0; i<${#1}; i++)); do
+        charmap[${1:i:1}]=${2:i:1}
+    done
+    while IFS= read -r line; do
+        trans=""
+        for ((i=0; i<${#line}; i++)); do
+            char=${line:i:1}
+            if [[ -n ${charmap[$char]} ]]; then
+                trans+=${charmap[$char]}
+            else
+                trans+=$char
+            fi
+        done
+        echo "$trans"
+    done
+}
+
+txt="The five boxing wizards jump quickly."
+enc=$(caesar -e -n 5 "$txt")
+dec=$(caesar -d -n 5 "$enc")
+
+echo "original:  $txt"
+echo "encrypted: $enc"
+echo "decrypted: $dec"