tail - npm Package Compare versions

Comparing version 2.1.1 to 2.2.0

lib/tail.js

@@ -24,6 +24,6 @@ let events = require(`events`)
         this.flushAtEOF = options.flushAtEOF || false;
-        this.encoding = options.encoding || `utf-8`;
+        this.encoding = options.encoding || 'utf-8';
         const fromBeginning = options.fromBeginning || false;
+        this.nLines = options.nLines || undefined;
 
-
         this.logger.info(`Tail starting...`)
@@ -53,10 +53,20 @@ this.logger.info(`filename: ${this.filename}`);
         this.logger.info(`fromBeginning: ${fromBeginning}`);
-        let startingPos = undefined;
+        let startingCursor;
         if (fromBeginning) {
-            startingPos = 0;
-            //if fromBeginning triggers a check for content to flush the existing file
-            //without waiting for a new appended line
-            this.change(this.filename);
-        } 
-        this.watch(startingPos);
+            startingCursor = 0;
+        } else if (this.nLines !== undefined) {
+            const data = fs.readFileSync(this.filename, {
+                flag: 'r',
+                encoding:this.encoding
+              });            
+            const tokens = data.split(this.separator);
+            const dropLastToken = (tokens[tokens.length-1] === '') ? 1:0;//if the file end with empty line ignore line NL
+            const match = data.match(new RegExp(`(?:[^\r\n]*[\r]{0,1}\n){${tokens.length - this.nLines - dropLastToken}}`));
+            startingCursor = (match && match.length) ? Buffer.byteLength(match[0], this.encoding) : this.latestPosition();
+        } else {
+            startingCursor = this.latestPosition() ;
+        }
+        if (startingCursor === undefined) throw new Error("Tail can't initialize.");
+        const flush = fromBeginning || (this.nLines != undefined);
+        this.watch(startingCursor, flush);
     }
@@ -109,9 +119,9 @@
 
-    change(filename) {
+    change() {
         let p = this.latestPosition()
-        if (p < this.pos) {//scenario where text is not appended but it's actually a w+
-            this.pos = p
-        } else if (p > this.pos) {
-            this.queue.push({ start: this.pos, end: p});
-            this.pos = p
+        if (p < this.currentCursorPos) {//scenario where text is not appended but it's actually a w+
+            this.currentCursorPos = p
+        } else if (p > this.currentCursorPos) {
+            this.queue.push({ start: this.currentCursorPos, end: p});
+            this.currentCursorPos = p
             if (this.queue.length == 1) {
@@ -123,6 +133,4 @@ this.internalDispatcher.emit("next");
 
-    watch(startingPos) {
-        if (this.isWatching) {
-            return
-        }
+    watch(startingCursor, flush) {
+        if (this.isWatching) return;
         this.logger.info(`filesystem.watch present? ${fs.watch != undefined}`);
@@ -132,3 +140,5 @@ this.logger.info(`useWatchFile: ${this.useWatchFile}`);
         this.isWatching = true;
-        this.pos = (startingPos === undefined) ? this.latestPosition() : startingPos;
+        this.currentCursorPos = startingCursor;
+        //force a file flush is either fromBegining or nLines flags were passed.
+        if (flush) this.change();
 
@@ -165,3 +175,3 @@ try {
                 this.rewatchId = setTimeout((() => { 
-                    this.watch(this.pos); 
+                    this.watch(this.currentCursorPos); 
                 }), 1000);
@@ -179,3 +189,3 @@ } else {
         if (e === 'change') {
-            this.change(this.filename);
+            this.change();
         } else if (e === 'rename') {
@@ -188,3 +198,3 @@ this.rename(evtFilename);
         if (curr.size > prev.size) {
-            this.pos = curr.size;    //Update this.pos so that a consumer can determine if entire file has been handled
+            this.currentCursorPos = curr.size;    //Update this.currentCursorPos so that a consumer can determine if entire file has been handled
             this.queue.push({ start: prev.size, end: curr.size });
@@ -191,0 +201,0 @@ if (this.queue.length == 1) {

package.json

@@ -17,3 +17,3 @@ {
   ],
-  "version": "2.1.1",
+  "version": "2.2.0",
   "homepage": "https://www.lucagrulla.com/node-tail",
@@ -20,0 +20,0 @@ "repository": {

README.md

@@ -75,12 +75,13 @@ # Tail
 
-* `separator`:  the line separator token (default: `/[\r]{0,1}\n/` to handle linux/mac (9+)/windows). Pass null if your file is binary there's no line separator.
+* `separator`:  the line separator token (default: `/[\r]{0,1}\n/` to handle linux/mac (9+)/windows). Pass `null` for is binary files with no line separator.
 * `fsWatchOptions`: the full set of options that can be passed to `fs.watch` as per node documentation (default: {}).
-* `fromBeginning`: forces the tail of the file from the very beginning of it instead of from the first new line that will be appended (default: `false`).
-* `follow`: simulate `tail -F` option. In the case the file is moved/renamed (or logrotated), if set to `true` `tail` will try to start tailing again after a 1 second delay, if set to `false` it will just emit an error event (default: `true`).
-* `logger`: a logger object(default: no logger). The passed logger has to respond to two methods:
+* `fromBeginning`:  tail from the beginning of the file (default: `false`). If `fromBeginning` is true `nLines` will be ignored.
+* `follow`: simulate `tail -F` option. In the case the file is moved/renamed/logrotated, if set to `true`  will start tailing again after a 1 second delay; if set to `false` it will  emit an error event (default: `true`).
+* `logger`: a logger object(default: no logger). The passed logger should follow the folliwing signature:
   * `info([data][, ...])`
   * `error([data][, ...])`
-* `useWatchFile`: if set to `true` will force the use of `fs.watchFile` rather than delegating to the library the choice between `fs.watch` and `fs.watchFile` (default: `false`).
-* `encoding`: the encoding of the file to tail (default:`utf-8`).
-* `flushAtEOF`: set to `true` if you want to force flush of content when end of file is reached. Particularly useful when there's no separator character at the end of the file (default: `false`).
+* `nLines`: tail from the last n lines. (default: `undefined`). Ignored if `fromBeginning` is set to `true`. 
+* `useWatchFile`: if set to `true` will force the use of `fs.watchFile` over delegating to the library the choice between `fs.watch` and `fs.watchFile` (default: `false`).
+* `encoding`: the file encoding (default:`utf-8`).
+* `flushAtEOF`: set to `true` to force flush of content when end of file is reached. Useful when there's no separator character at the end of the file (default: `false`).
 
@@ -109,3 +110,3 @@ ## Emitted events
 
-Tail is written in plain ES6.Pull Requests are welcome.
+Tail is written in ES6. Pull Requests are welcome.
 
@@ -115,3 +116,3 @@ ## History
 Tail was born as part of a data firehose. Read about it [here](https://www.lucagrulla.com/posts/building-a-firehose-with-nodejs/).
-Tail original version was written in [CoffeeScript](https://coffeescript.org/). Since 2020 it's pure ES6.
+Tail original version was written in [CoffeeScript](https://coffeescript.org/). Since December 2020 it's pure ES6.
 
@@ -118,0 +119,0 @@ ## License

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License

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Found 1 instance in 1 package

Fixed alerts

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License

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Major refactor

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Package has recently undergone a major refactor. It may be unstable or indicate significant internal changes. Use caution when updating to versions that include significant changes.

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Improved metrics

Total package byte prevSize

13712

increased by6.96%

Lines of code

196

increased by5.95%

Number of lines in readme file

119

increased by0.85%

Number of medium supply chain risk alerts

0

decreased by-100%

No dependency changes