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child_process: add shell option to spawn()
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This commit adds a shell option, to spawn() and spawnSync(). This
option allows child processes to be spawned with or without a
shell. The option also allows a custom shell to be defined, for
compatibility with exec()'s shell option.

Fixes: #1009
PR-URL: #4598
Reviewed-By: Ben Noordhuis <[email protected]>
Reviewed-By: James M Snell <[email protected]>
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cjihrig authored and MylesBorins committed Jan 24, 2017
1 parent 416b6a7 commit f3f57be
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Showing 4 changed files with 144 additions and 29 deletions.
19 changes: 14 additions & 5 deletions doc/api/child_process.md
Original file line number Diff line number Diff line change
Expand Up @@ -77,11 +77,12 @@ The importance of the distinction between `child_process.exec()` and
`child_process.execFile()` can vary based on platform. On Unix-type operating
systems (Unix, Linux, OSX) `child_process.execFile()` can be more efficient
because it does not spawn a shell. On Windows, however, `.bat` and `.cmd`
files are not executable on their own without a terminal and therefore cannot
be launched using `child_process.execFile()` (or even `child_process.spawn()`).
When running on Windows, `.bat` and `.cmd` files can only be invoked using
either `child_process.exec()` or by spawning `cmd.exe` and passing the `.bat`
or `.cmd` file as an argument (which is what `child_process.exec()` does).
files are not executable on their own without a terminal, and therefore cannot
be launched using `child_process.execFile()`. When running on Windows, `.bat`
and `.cmd` files can be invoked using `child_process.spawn()` with the `shell`
option set, with `child_process.exec()`, or by spawning `cmd.exe` and passing
the `.bat` or `.cmd` file as an argument (which is what the `shell` option and
`child_process.exec()` do).

```js
// On Windows Only ...
Expand Down Expand Up @@ -303,6 +304,10 @@ added: v0.1.90
[`options.detached`][])
* `uid` {Number} Sets the user identity of the process. (See setuid(2).)
* `gid` {Number} Sets the group identity of the process. (See setgid(2).)
* `shell` {Boolean|String} If `true`, runs `command` inside of a shell. Uses
'/bin/sh' on UNIX, and 'cmd.exe' on Windows. A different shell can be
specified as a string. The shell should understand the `-c` switch on UNIX,
or `/s /c` on Windows. Defaults to `false` (no shell).
* return: {ChildProcess}

The `child_process.spawn()` method spawns a new process using the given
Expand Down Expand Up @@ -635,6 +640,10 @@ added: v0.11.12
* `maxBuffer` {Number} largest amount of data (in bytes) allowed on stdout or
stderr - if exceeded child process is killed
* `encoding` {String} The encoding used for all stdio inputs and outputs. (Default: 'buffer')
* `shell` {Boolean|String} If `true`, runs `command` inside of a shell. Uses
'/bin/sh' on UNIX, and 'cmd.exe' on Windows. A different shell can be
specified as a string. The shell should understand the `-c` switch on UNIX,
or `/s /c` on Windows. Defaults to `false` (no shell).
* return: {Object}
* `pid` {Number} Pid of the child process
* `output` {Array} Array of results from stdio output
Expand Down
53 changes: 29 additions & 24 deletions lib/child_process.js
Original file line number Diff line number Diff line change
Expand Up @@ -71,7 +71,8 @@ exports._forkChild = function(fd) {


function normalizeExecArgs(command /*, options, callback*/) {
var file, args, options, callback;
let options;
let callback;

if (typeof arguments[1] === 'function') {
options = undefined;
Expand All @@ -81,25 +82,12 @@ function normalizeExecArgs(command /*, options, callback*/) {
callback = arguments[2];
}

if (process.platform === 'win32') {
file = process.env.comspec || 'cmd.exe';
args = ['/s', '/c', '"' + command + '"'];
// Make a shallow copy before patching so we don't clobber the user's
// options object.
options = util._extend({}, options);
options.windowsVerbatimArguments = true;
} else {
file = '/bin/sh';
args = ['-c', command];
}

if (options && options.shell)
file = options.shell;
// Make a shallow copy so we don't clobber the user's options object.
options = Object.assign({}, options);
options.shell = typeof options.shell === 'string' ? options.shell : true;

return {
cmd: command,
file: file,
args: args,
file: command,
options: options,
callback: callback
};
Expand All @@ -109,7 +97,6 @@ function normalizeExecArgs(command /*, options, callback*/) {
exports.exec = function(command /*, options, callback*/) {
var opts = normalizeExecArgs.apply(null, arguments);
return exports.execFile(opts.file,
opts.args,
opts.options,
opts.callback);
};
Expand All @@ -123,7 +110,8 @@ exports.execFile = function(file /*, args, options, callback*/) {
maxBuffer: 200 * 1024,
killSignal: 'SIGTERM',
cwd: null,
env: null
env: null,
shell: false
};

// Parse the optional positional parameters.
Expand Down Expand Up @@ -153,6 +141,7 @@ exports.execFile = function(file /*, args, options, callback*/) {
env: options.env,
gid: options.gid,
uid: options.uid,
shell: options.shell,
windowsVerbatimArguments: !!options.windowsVerbatimArguments
});

Expand Down Expand Up @@ -331,7 +320,23 @@ function normalizeSpawnArguments(file /*, args, options*/) {
else if (options === null || typeof options !== 'object')
throw new TypeError('options argument must be an object');

options = util._extend({}, options);
// Make a shallow copy so we don't clobber the user's options object.
options = Object.assign({}, options);

if (options.shell) {
const command = [file].concat(args).join(' ');

if (process.platform === 'win32') {
file = typeof options.shell === 'string' ? options.shell :
process.env.comspec || 'cmd.exe';
args = ['/s', '/c', '"' + command + '"'];
options.windowsVerbatimArguments = true;
} else {
file = typeof options.shell === 'string' ? options.shell : '/bin/sh';
args = ['-c', command];
}
}

args.unshift(file);

var env = options.env || process.env;
Expand Down Expand Up @@ -492,12 +497,12 @@ function execFileSync(/*command, args, options*/) {
exports.execFileSync = execFileSync;


function execSync(/*command, options*/) {
function execSync(command /*, options*/) {
var opts = normalizeExecArgs.apply(null, arguments);
var inheritStderr = opts.options ? !opts.options.stdio : true;

var ret = spawnSync(opts.file, opts.args, opts.options);
ret.cmd = opts.cmd;
var ret = spawnSync(opts.file, opts.options);
ret.cmd = command;

if (inheritStderr && ret.stderr)
process.stderr.write(ret.stderr);
Expand Down
64 changes: 64 additions & 0 deletions test/parallel/test-child-process-spawn-shell.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,64 @@
'use strict';
const common = require('../common');
const assert = require('assert');
const cp = require('child_process');

// Verify that a shell is, in fact, executed
const doesNotExist = cp.spawn('does-not-exist', {shell: true});

assert.notEqual(doesNotExist.spawnfile, 'does-not-exist');
doesNotExist.on('error', common.fail);
doesNotExist.on('exit', common.mustCall((code, signal) => {
assert.strictEqual(signal, null);

if (common.isWindows)
assert.strictEqual(code, 1); // Exit code of cmd.exe
else
assert.strictEqual(code, 127); // Exit code of /bin/sh
}));

// Verify that passing arguments works
const echo = cp.spawn('echo', ['foo'], {
encoding: 'utf8',
shell: true
});
let echoOutput = '';

assert.strictEqual(echo.spawnargs[echo.spawnargs.length - 1].replace(/"/g, ''),
'echo foo');
echo.stdout.on('data', (data) => {
echoOutput += data;
});
echo.on('close', common.mustCall((code, signal) => {
assert.strictEqual(echoOutput.trim(), 'foo');
}));

// Verify that shell features can be used
const cmd = common.isWindows ? 'echo bar | more' : 'echo bar | cat';
const command = cp.spawn(cmd, {
encoding: 'utf8',
shell: true
});
let commandOutput = '';

command.stdout.on('data', (data) => {
commandOutput += data;
});
command.on('close', common.mustCall((code, signal) => {
assert.strictEqual(commandOutput.trim(), 'bar');
}));

// Verify that the environment is properly inherited
const env = cp.spawn(`"${process.execPath}" -pe process.env.BAZ`, {
env: Object.assign({}, process.env, {BAZ: 'buzz'}),
encoding: 'utf8',
shell: true
});
let envOutput = '';

env.stdout.on('data', (data) => {
envOutput += data;
});
env.on('close', common.mustCall((code, signal) => {
assert.strictEqual(envOutput.trim(), 'buzz');
}));
37 changes: 37 additions & 0 deletions test/parallel/test-child-process-spawnsync-shell.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,37 @@
'use strict';
const common = require('../common');
const assert = require('assert');
const cp = require('child_process');

// Verify that a shell is, in fact, executed
const doesNotExist = cp.spawnSync('does-not-exist', {shell: true});

assert.notEqual(doesNotExist.file, 'does-not-exist');
assert.strictEqual(doesNotExist.error, undefined);
assert.strictEqual(doesNotExist.signal, null);

if (common.isWindows)
assert.strictEqual(doesNotExist.status, 1); // Exit code of cmd.exe
else
assert.strictEqual(doesNotExist.status, 127); // Exit code of /bin/sh

// Verify that passing arguments works
const echo = cp.spawnSync('echo', ['foo'], {shell: true});

assert.strictEqual(echo.args[echo.args.length - 1].replace(/"/g, ''),
'echo foo');
assert.strictEqual(echo.stdout.toString().trim(), 'foo');

// Verify that shell features can be used
const cmd = common.isWindows ? 'echo bar | more' : 'echo bar | cat';
const command = cp.spawnSync(cmd, {shell: true});

assert.strictEqual(command.stdout.toString().trim(), 'bar');

// Verify that the environment is properly inherited
const env = cp.spawnSync(`"${process.execPath}" -pe process.env.BAZ`, {
env: Object.assign({}, process.env, {BAZ: 'buzz'}),
shell: true
});

assert.strictEqual(env.stdout.toString().trim(), 'buzz');

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