feat(command): new command: tail()

README.md

@@ -302,6 +302,36 @@ containing the files if more than one file is given (a new line character is
 introduced between each file).
 
 
+### head([{'-n', \<num\>},] file [, file ...])
+### head([{'-n', \<num\>},] file_array)
+
+Examples:
+
+```javascript
+var str = head({'-n', 1}, 'file*.txt');
+var str = head('file1', 'file2');
+var str = head(['file1', 'file2']); // same as above
+```
+
+Output the first 10 lines of a file (or the first `<num>` if `-n` is
+specified)
+
+
+### tail([{'-n', \<num\>},] file [, file ...])
+### tail([{'-n', \<num\>},] file_array)
+
+Examples:
+
+```javascript
+var str = tail({'-n', 1}, 'file*.txt');
+var str = tail('file1', 'file2');
+var str = tail(['file1', 'file2']); // same as above
+```
+
+Output the last 10 lines of a file (or the last `<num>` if `-n` is
+specified)
+
+
 ### ShellString.prototype.to(file)
 
 Examples:
@@ -345,7 +375,7 @@ using the given search regex and replacement string or function. Returns the new
 
 
 ### sort([options,] file [, file ...])
-### sed([options,] file_array)
+### sort([options,] file_array)
 Available options:
 
 + `-r`: Reverse the result of comparisons

shell.js

@@ -62,6 +62,10 @@ exports.cat = common.wrap('cat', _cat, {idx: 1});
 var _head = require('./src/head');
 exports.head = common.wrap('head', _head, {idx: 1});
 
+//@include ./src/tail
+var _tail = require('./src/tail');
+exports.tail = common.wrap('tail', _tail, {idx: 1});
+
 // The below commands have been moved to common.ShellString(), and are only here
 // for generating the docs
 //@include ./src/to

src/common.js

@@ -101,7 +101,7 @@ var ShellString = function (stdout, stderr, code) {
   that.code = code;
   that.to    = function() {wrap('to', _to, {idx: 1}).apply(that.stdout, arguments); return that;};
   that.toEnd = function() {wrap('toEnd', _toEnd, {idx: 1}).apply(that.stdout, arguments); return that;};
-  ['cat', 'head', 'sed', 'sort', 'grep', 'exec'].forEach(function (cmd) {
+  ['cat', 'head', 'sed', 'sort', 'tail', 'grep', 'exec'].forEach(function (cmd) {
     that[cmd] = function() {return shell[cmd].apply(that.stdout, arguments);};
   });
   return that;

src/sort.js

@@ -32,7 +32,7 @@ function numericalCmp(a, b) {
 
 //@
 //@ ### sort([options,] file [, file ...])
-//@ ### sed([options,] file_array)
+//@ ### sort([options,] file_array)
 //@ Available options:
 //@
 //@ + `-r`: Reverse the result of comparisons

src/tail.js

@@ -0,0 +1,65 @@
+var common = require('./common');
+var fs = require('fs');
+
+//@
+//@ ### tail([{'-n', \<num\>},] file [, file ...])
+//@ ### tail([{'-n', \<num\>},] file_array)
+//@
+//@ Examples:
+//@
+//@ ```javascript
+//@ var str = tail({'-n', 1}, 'file*.txt');
+//@ var str = tail('file1', 'file2');
+//@ var str = tail(['file1', 'file2']); // same as above
+//@ ```
+//@
+//@ Output the last 10 lines of a file (or the last `<num>` if `-n` is
+//@ specified)
+function _tail(options, files) {
+  options = common.parseOptions(options, {
+    'n': 'numLines'
+  });
+  var tail = [];
+  var pipe = common.readFromPipe(this);
+
+  if (!files && !pipe)
+    common.error('no paths given');
+
+  var idx = 1;
+  if (options.numLines === true) {
+    idx = 2;
+    options.numLines = Number(arguments[1]);
+  } else if (options.numLines === false) {
+    options.numLines = 10;
+  }
+  options.numLines = -1 * Math.abs(options.numLines);
+  files = [].slice.call(arguments, idx);
+
+  if (pipe)
+    files.unshift('-');
+
+  var shouldAppendNewline = false;
+  files.forEach(function(file) {
+    if (!fs.existsSync(file) && file !== '-') {
+      common.error('no such file or directory: ' + file, true);
+      return;
+    }
+
+    var contents = file === '-' ? pipe : fs.readFileSync(file, 'utf8');
+
+    var lines = contents.split('\n');
+    if (lines[lines.length-1] === '') {
+      lines.pop();
+      shouldAppendNewline = true;
+    } else {
+      shouldAppendNewline = false;
+    }
+
+    tail = tail.concat(lines.slice(options.numLines));
+  });
+
+  if (shouldAppendNewline)
+    tail.push(''); // to add a trailing newline once we join
+  return new common.ShellString(tail.join('\n'), common.state.error, common.state.errorCode);
+}
+module.exports = _tail;

test/config.js

@@ -52,10 +52,11 @@ child.exec(JSON.stringify(process.execPath)+' '+file, function(err, stdout) {
 
 // Expands to directories by default
 var result = common.expand(['resources/*a*']);
-assert.equal(result.length, 4);
+assert.equal(result.length, 5);
 assert.ok(result.indexOf('resources/a.txt') > -1);
 assert.ok(result.indexOf('resources/badlink') > -1);
 assert.ok(result.indexOf('resources/cat') > -1);
+assert.ok(result.indexOf('resources/head') > -1);
 assert.ok(result.indexOf('resources/external') > -1);
 
 // Check to make sure options get passed through (nodir is an example)

test/tail.js

@@ -0,0 +1,105 @@
+var shell = require('..');
+
+var assert = require('assert');
+var fs = require('fs');
+
+shell.config.silent = true;
+
+shell.rm('-rf', 'tmp');
+shell.mkdir('tmp');
+
+var result;
+
+//
+// Invalids
+//
+
+result = shell.tail();
+assert.ok(shell.error());
+assert.equal(result.code, 1);
+
+assert.equal(fs.existsSync('/asdfasdf'), false); // sanity check
+result = shell.tail('/adsfasdf'); // file does not exist
+assert.ok(shell.error());
+assert.equal(result.code, 1);
+
+//
+// Valids
+//
+
+var bottomOfFile1 = ['file1 50', 'file1 49', 'file1 48', 'file1 47', 'file1 46',
+                     'file1 45', 'file1 44', 'file1 43', 'file1 42', 'file1 41',
+                     'file1 40', 'file1 39', 'file1 38', 'file1 37', 'file1 36',
+                     'file1 35', 'file1 34', 'file1 33', 'file1 32', 'file1 31'];
+var bottomOfFile2 = ['file2 50', 'file2 49', 'file2 48', 'file2 47', 'file2 46',
+                     'file2 45', 'file2 44', 'file2 43', 'file2 42', 'file2 41',
+                     'file2 40', 'file2 39', 'file2 38', 'file2 37', 'file2 36',
+                     'file2 35', 'file2 34', 'file2 33', 'file2 32', 'file2 31'];
+
+// simple
+result = shell.tail('resources/head/file1.txt');
+assert.equal(shell.error(), null);
+assert.equal(result.code, 0);
+assert.equal(result, bottomOfFile1.slice(0, 10).reverse().join('\n')+'\n');
+
+// multiple files
+result = shell.tail('resources/head/file2.txt', 'resources/head/file1.txt');
+assert.equal(shell.error(), null);
+assert.equal(result.code, 0);
+assert.equal(result, bottomOfFile2.slice(0, 10).reverse().concat(
+                         bottomOfFile1.slice(0, 10).reverse()
+                     ).join('\n')+'\n');
+
+// multiple files, array syntax
+result = shell.tail(['resources/head/file2.txt', 'resources/head/file1.txt']);
+assert.equal(shell.error(), null);
+assert.equal(result.code, 0);
+assert.equal(result, bottomOfFile2.slice(0, 10).reverse().concat(
+                         bottomOfFile1.slice(0, 10).reverse()
+                     ).join('\n')+'\n');
+
+// reading more lines than are in the file (no trailing newline)
+result = shell.tail('resources/file2', 'resources/file1');
+assert.equal(shell.error(), null);
+assert.equal(result.code, 0);
+assert.equal(result, 'test2\ntest1'); // these files only have one line (no \n)
+
+// reading more lines than are in the file (with trailing newline)
+result = shell.tail('resources/head/shortfile2', 'resources/head/shortfile1');
+assert.equal(shell.error(), null);
+assert.equal(result.code, 0);
+assert.equal(result, 'short2\nshort1\n'); // these files only have one line (with \n)
+
+// Globbed file
+result = shell.tail('resources/head/file?.txt');
+assert.equal(shell.error(), null);
+assert.equal(result.code, 0);
+assert.equal(result, bottomOfFile1.slice(0, 10).reverse().concat(
+                         bottomOfFile2.slice(0, 10).reverse()
+                     ).join('\n')+'\n');
+
+// With `'-n' <num>` option
+result = shell.tail('-n', 4, 'resources/head/file2.txt', 'resources/head/file1.txt');
+assert.equal(shell.error(), null);
+assert.equal(result.code, 0);
+assert.equal(result, bottomOfFile2.slice(0, 4).reverse().concat(
+                         bottomOfFile1.slice(0, 4).reverse()
+                     ).join('\n')+'\n');
+
+// With `{'-n': <num>}` option
+result = shell.tail({'-n': 4}, 'resources/head/file2.txt', 'resources/head/file1.txt');
+assert.equal(shell.error(), null);
+assert.equal(result.code, 0);
+assert.equal(result, bottomOfFile2.slice(0, 4).reverse().concat(
+                         bottomOfFile1.slice(0, 4).reverse()
+                     ).join('\n')+'\n');
+
+// negative values are the same as positive values
+result = shell.tail('-n', -4, 'resources/head/file2.txt', 'resources/head/file1.txt');
+assert.equal(shell.error(), null);
+assert.equal(result.code, 0);
+assert.equal(result, bottomOfFile2.slice(0, 4).reverse().concat(
+                         bottomOfFile1.slice(0, 4).reverse()
+                     ).join('\n')+'\n');
+
+shell.exit(123);