modified: docs/shells/bash.md

docs/shells/bash.md

@@ -1,5 +1,54 @@
 # Bash
 
+## arrays
+
+``` bash
+# creates an array variable
+ORPHANS=()
+
+# checks length
+if [[ ${#ORPHANS[@]} -eq 0 ]]; then
+    echo "No orphans found."
+else
+    echo "orphans:"
+    printf "%s\n" "${ORPHANS[@]}"
+fi
+```
+
+## associative array
+
+an data structure that lets you store key → value pairs
+
+``` bash
+# clean if already been used
+unset PV_PATHS
+# declare an associative array, an data structure that lets you store key → value pairs
+declare -A PV_PATHS
+for name in $(kubectl get pv -o jsonpath='{.items[*].metadata.name}'); do
+    path=$(kubectl get pv ${name} -o jsonpath='{.spec.local.path}' 2>/dev/null)
+    # check if path is no empty
+    [[ -n "${path}" ]] && PV_PATHS["${name}"]="${path}"
+done
+# print only keys
+echo
+echo "All Keys:"
+printf "%s\n" "${!PV_PATHS[@]}"
+
+echo
+echo "All Values:"
+# print only values
+printf "%s\n" "${PV_PATHS[@]}"
+
+echo
+echo "Keys|Values:"
+# print all
+for key in "${!PV_PATHS[@]}"; do
+    printf "%s|%s\n" "$key" "${PV_PATHS[$key]}"
+done
+```
+
+## misc
+
 ```bash
 #!/bin/bash
 script_directory="$(dirname "$(readlink -f "$0")")"