ptbrowne · July 23, 2019 08:28 · Jul 23, 2019 · Jul 23, 2019 · Jul 23, 2019 · Jul 23, 2019
diff --git a/README.md b/README.md
@@ -9,12 +9,12 @@ immediately.
 ## Installation
 
 ```
-wget <THIS_GIST> -O cache.js
-ln -s $(pwd)/cache.js ~/bin/cache
+wget https://gist.github.com/ptbrowne/f697899b2212757f4b857d794e48ea30/raw/9b6e96506e2c3b0c64bceea70302f5597c452272/cache.js -O ~/bin/cache
+chmod +x ~/bin/cache
 ```
 
 I used `~/bin/` because this directory is already in my `PATH` but you can use any directory that
-is in your PATH.
+is in your `PATH`.
 
 ## Usage
 

diff --git a/README.md b/README.md
@@ -27,9 +27,8 @@ is in your PATH.
 
 ## How does it work
 
-`cache` makes a key out of all the arguments, hashes it to make a `<key>`, and looks for /tmp/`<key>`. If the
-file exists, it outputs its content (max length 10Mo).
+`cache` makes an array out of all the arguments (name + index), JSON stringifies it, hashes it to make a `<key>`, and looks for /tmp/`<key>`. If the file exists, it outputs its content (max length 10Mo).
 
  Additionally, an extra step is taken to handle file arguments. For each argument, we check a file with the same
- name exists and if it exists, the modification time is added to the key. If it changes, the `<key>` changes
- and the result of the command is recomputed.
+ name exists and if it exists, the modification time is added to information of the argument. If the file changes,
+ the `<key>` changes and the result of the command is recomputed.
diff --git a/README.md b/README.md
@@ -1,6 +1,7 @@
 If you deal with commands that can take several seconds but always return the same result
 and you need to transform the result with pipe chain (jq / grep / awk), it can be annoying
-to always wait those seconds when you know the result has not changed.
+to wait for those seconds while you incrementally build the command, when you know the
+result has not changed.
 
 `cache.js` can help you by caching the result of the command to /tmp and returning the result
 immediately.

diff --git a/README.md b/README.md
@@ -0,0 +1,34 @@
+If you deal with commands that can take several seconds but always return the same result
+and you need to transform the result with pipe chain (jq / grep / awk), it can be annoying
+to always wait those seconds when you know the result has not changed.
+
+`cache.js` can help you by caching the result of the command to /tmp and returning the result
+immediately.
+
+## Installation
+
+```
+wget <THIS_GIST> -O cache.js
+ln -s $(pwd)/cache.js ~/bin/cache
+```
+
+I used `~/bin/` because this directory is already in my `PATH` but you can use any directory that
+is in your PATH.
+
+## Usage
+
+`cache` "decorates" the command you give it.
+
+```patch
+- ./long-command input-file.json --my-arg 
++ cache ./long-command input-file.json --my-arg 
+```
+
+## How does it work
+
+`cache` makes a key out of all the arguments, hashes it to make a `<key>`, and looks for /tmp/`<key>`. If the
+file exists, it outputs its content (max length 10Mo).
+
+ Additionally, an extra step is taken to handle file arguments. For each argument, we check a file with the same
+ name exists and if it exists, the modification time is added to the key. If it changes, the `<key>` changes
+ and the result of the command is recomputed.
diff --git a/cache.js b/cache.js
@@ -0,0 +1,31 @@
+#!/usr/bin/env node
+
+const fs = require('fs')
+const child_process = require('child_process')
+const crypto = require('crypto')
+const args = process.argv.slice(2)
+const withCacheInfo = args.map((argName, argIndex) => {
+    return {
+        argName,
+        argIndex,
+        mtime: fs.existsSync(argName) ? fs.statSync(argName).mtime : undefined
+    }
+})
+
+const cacheKey = JSON.stringify(withCacheInfo, null, 2)
+const hash = crypto.createHash('md5').update(cacheKey).digest("hex")
+const filename =`/tmp/${hash}-cache`
+
+if (fs.existsSync(filename)) {
+    console.log(fs.readFileSync(filename).toString())
+} else {
+    child_process.exec(args.join(' '), { maxBuffer: 1024*1024*1024 }, (error, stdout) => {
+      if (error) {
+        console.error(error)
+        process.exit(1)
+      } else {
+        fs.writeFileSync(filename, stdout)
+        console.log(stdout) 
+      }
+    })
+}