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express-server/node_modules/safe-replace/README.md

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+safe-replace
+============
+
+A micro-module for safely replacing a file.
+
+This is intended to be generally safe even when a function that writes a file
+is accidentally called twice (as may happen with node cluster).
+
+Commandline Reference
+---------------------
+
+If I want to safely replace a file with a new version, I would do so like this:
+
+```bash
+# create the new version
+touch keep.txt.RANDOM.tmp
+
+# remove the previous backup
+rm -f keep.txt.bak
+
+# move the current version to the backup
+mv keep.txt keep.txt.bak
+
+# move the new version to the current
+mv keep.txt.RANDOM.tmp keep.txt
+```
+
+If `keep.txt` became corrupt and I wanted to use the backup,
+I would do this:
+
+```bash
+# copy the backup to the new version
+rsync keep.txt.bak keep.txt
+```
+
+In Node
+-------
+
+I ported that proccess to node.
+
+```
+sfs.writeFileAsync
+sfs.stageAsync
+sfs.commitAsync
+sfs.revertAsync
+```
+
+```js
+// default behavior is to concat (filename + '.' + rnd() + '.tmp')
+var safeReplace = require('safe-replace').create({ tmp: 'tmp', bak: 'bak' });
+
+var data = new Buffer('A priceless document');
+safeReplace.writeFileAsync('keep.txt', data, 'ascii').then(function () {
+  fs.readdir('.', function (nodes) {
+    console.log('file system nodes', nodes);
+    // keep.txt
+    // keep.txt.bak
+  });
+});
+
+// let's say I want to write a tmp file and not commit it... weird
+safeReplace.stageAsync('keep.txt', data, 'ascii').then(function (tmpname) {
+  fs.readdir('.', function (nodes) {
+    console.log('file system nodes', nodes);
+    // keep.txt.ac71teh8mja.tmp
+  });
+});
+
+// let's say I wrote keep.txt.x7t7sq926.tmp with my own mechanism
+safeReplace.commitAsync('keep.txt.x7t7sq926.tmp', 'keep.txt').then(function () {
+  fs.readdir('.', function (nodes) {
+    console.log('file system nodes', nodes);
+    // keep.txt
+    // keep.txt.bak
+  });
+});
+
+// let's say I want to revert the file from the '.bak'
+safeReplace.revertAsync('keep.txt').then(function () {
+  fs.readdir('.', function (nodes) {
+    console.log('file system nodes', nodes);
+    // keep.txt
+    // keep.txt.bak
+  });
+});
+```