Implement --version and add Homebrew install to README

README.md

@@ -1,5 +1,7 @@
 # aws-session
 
+Manage shell sessions with temporary AWS credentials
+
 [![Build Status](https://travis-ci.org/ksperling/aws-session.svg?branch=master)](https://travis-ci.org/ksperling/aws-session)
 [![Code Climate](https://codeclimate.com/github/ksperling/aws-session/badges/gpa.svg)](https://codeclimate.com/github/ksperling/aws-session)
 
@@ -11,9 +13,11 @@ In supported shells (`bash`, `zsh`) it also enhances the shell prompt to display
 
 ## Installation
 
-Before using `aws-session`, you must have the [AWS CLI](https://aws.amazon.com/cli/) installed (through whatever [method](http://docs.aws.amazon.com/cli/latest/userguide/installing.html) you choose) on your PATH and configured (through `aws configure` or manually).
+On OS X, the easiest way to install `aws-session` is via [Homebrew](https://brew.sh/): `brew install ksperling/tap/aws-session`.
 
-`aws-session` itself is a stand-alone shell script, just [download the script](https://raw.githubusercontent.com/ksperling/aws-session/master/aws-session) and place it somewhere on your PATH, e.g. in `/usr/local/bin`.
+Otherwise a manual install is straightforward: just [download the script](https://raw.githubusercontent.com/ksperling/aws-session/master/aws-session) and place it somewhere on your PATH, e.g. in `/usr/local/bin`.
+
+Before using `aws-session`, you must have the [AWS CLI](https://aws.amazon.com/cli/) installed (through whatever [method](http://docs.aws.amazon.com/cli/latest/userguide/installing.html) you choose) on your PATH and configured (through `aws configure` or manually).
 
 ## Usage
 

aws-session

@@ -1,5 +1,6 @@
 #!/bin/bash
 # aws-session: Run a shell environment with AWS MFA credentials
+version=HEAD
 set -o pipefail
 
 function main() {
@@ -20,11 +21,13 @@ function main() {
         shift 2
         ;;
       --debug) export AWS_SESSION_DEBUG=1; shift;;
+      --version) version; exit 0;;
       --help) echo "$usage
 Options:
   --profile PROFILE            set profile from ~/.aws, see AWS_DEFAULT_PROFILE
   --session-duration SECONDS   requested session validity (default 12 hours)
   --debug                      enable debug output
+  --version                    display version information
   --help                       display this help text
 
 Commands:
@@ -50,6 +53,19 @@ Environment variables:
   esac
 }
 
+function version() {
+  local cli="$(command aws --version 2>&1)"
+  if [[ "$cli" =~ ^aws-cli/([0-9]+)\.([0-9]+)\. ]]; then
+    echo "aws-session/${version} ${cli}"
+    local maj="${BASH_REMATCH[1]}" min="${BASH_REMATCH[2]}"
+    if [[ "$maj" -lt 1 || "$maj" -eq 1 && "$min" -lt 11 ]]; then
+      info "Warning: aws-session may not work correctly with aws-cli < 1.11"
+    fi
+  else
+    echo "aws-session/${version} aws-cli/unknown"
+  fi
+}
+
 function session_exec() { # cmd args ...
   [[ $# -ge 1 ]] || fail 1 "Usage: ${0##*/} exec COMMAND [ARGS...]"
   establish_mfa_session || return $?