add ability to modify display of cluster and namespace

README.md

@@ -127,6 +127,8 @@ the following environment variables:
 | `KUBE_PS1_SEPARATOR` | | | Separator between symbol and cluster name |
 | `KUBE_PS1_DIVIDER` | `:` | Separator between cluster and namespace |
 | `KUBE_PS1_SUFFIX` | `)` | Prompt closing character |
+| `KUBE_PS1_CLUSTER_FUNCTION` | No default, must be user supplied | Function to customize how cluster is displayed |
+| `KUBE_PS1_NAMESPACE_FUNCTION` | No default, must be user supplied | Function to customize how namespace is displayed |
 
 For terminals that do not support UTF-8, the symbol will be replaced with the
 string `k8s`.
@@ -168,6 +170,37 @@ black, red, green, yellow, blue, magenta, cyan
 256 colors are available by specifying the numerical value as the variable
 argument.
 
+## Customize display of cluster name and namespace
+
+You can change how the cluster name and namespace are displayed using the `KUBE_PS1_CLUSTER_FUNCTION` and `KUBE_PS1_NAMESPACE_FUNCTION` variables respectively.
+
+For the following examples let's assume the following:
+
+cluster name: `sandbox.k8s.example.com`
+namespace: `alpha`
+
+If you're using domain style cluster names, your prompt will get quite long very quickly. Let's say you only want to display the first portion of the cluster name (`sandbox`), you could do that by adding the following:
+
+```
+function get_cluster_short() {
+  echo "$1" | cut -d . -f1
+}
+
+KUBE_PS1_CLUSTER_FUNCTION=get_cluster_short
+```
+
+The same pattern can be followed to customize the display of the namespace. Let's say you would prefer the namespace to be displayed in all uppercase (`ALPHA`), here's one way you could do that:
+
+```
+function get_namespace_upper() {
+    echo "$1" | tr '[:lower:]' '[:upper:]'
+}
+
+export KUBE_PS1_NAMESPACE_FUNCTION=get_namespace_upper
+```
+
+In both cases, the variable is set to the name of the function, and you must have defined the function in your shell configuration before kube_ps1 is called. The function must accept a single parameter and echo out the final value.
+
 ### Bug Reports and shell configuration
 
 Due to the vast ways of customizing the shell, please try the prompt with a

kube-ps1.sh

@@ -39,6 +39,8 @@ KUBE_PS1_KUBECONFIG_CACHE="${KUBECONFIG}"
 KUBE_PS1_DISABLE_PATH="${HOME}/.kube/kube-ps1/disabled"
 KUBE_PS1_UNAME=$(uname)
 KUBE_PS1_LAST_TIME=0
+KUBE_PS1_CLUSTER_FUNCTION="${KUBE_PS1_CLUSTER_FUNCTION}"
+KUBE_PS1_NAMESPACE_FUNCTION="${KUBE_PS1_NAMESPACE_FUNCTION}"
 
 # Determine our shell
 if [ "${ZSH_VERSION-}" ]; then
@@ -235,6 +237,11 @@ _kube_ps1_get_context_ns() {
   fi
 
   KUBE_PS1_CONTEXT="$(${KUBE_PS1_BINARY} config current-context 2>/dev/null)"
+
+  if [[ ! -z "${KUBE_PS1_CLUSTER_FUNCTION}" ]]; then
+    KUBE_PS1_CONTEXT=$($KUBE_PS1_CLUSTER_FUNCTION $KUBE_PS1_CONTEXT)
+  fi
+
   if [[ -z "${KUBE_PS1_CONTEXT}" ]]; then
     KUBE_PS1_CONTEXT="N/A"
     KUBE_PS1_NAMESPACE="N/A"
@@ -243,6 +250,11 @@ _kube_ps1_get_context_ns() {
     KUBE_PS1_NAMESPACE="$(${KUBE_PS1_BINARY} config view --minify --output 'jsonpath={..namespace}' 2>/dev/null)"
     # Set namespace to 'default' if it is not defined
     KUBE_PS1_NAMESPACE="${KUBE_PS1_NAMESPACE:-default}"
+
+    if [[ ! -z "${KUBE_PS1_NAMESPACE_FUNCTION}" ]]; then
+        KUBE_PS1_NAMESPACE=$($KUBE_PS1_NAMESPACE_FUNCTION $KUBE_PS1_NAMESPACE)
+    fi
+
   fi
 }