问题
So I'm making a Gnome Shell extension. And I want to be able to run some command with a pipe. (The command is actually "xrandr --query | awk 'something'", but that is off topic)
So, what I have done so far is
GLib.spawn_async_with_pipes(null,
['/usr/bin/xrandr', '--query', '|', 'awk...'], null,
GLib.SpawnFlags.DO_NOT_REAP_CHILD, null);
But it doesn't work! I can't find any example of running a command in a gnome extensions with a pipe.
Do I have to write "|" in the command like I did ?
回答1:
spawn_async_with_pipes doesn't do what you want (in a simple way). It return the pipes to process with it. You could do it with two call and connecting but it will be a little bit complex.
A simple way to keep the exact syntax is to call a shell which will do the pipe processing with the help of this answer which give a way to call a command, I wrote the following code which call the shell (bash for this case) with correct arguments
const Util = imports.misc.util;
Util.spawn(['/bin/bash', '-c', "xrandr --query | awk 'something'"])
回答2:
I implemented a TerminalReader class some time ago in a Cinnamon Applet: https://github.com/lestcape/Configurable-Menu/blob/OwnAPI/configurableMenu%40lestcape/pakagesManager.js#L31
This class is now used in other places also, so you have more examples to underestand it better: https://github.com/search?l=JavaScript&q=TerminalReader&type=Code&utf8=%E2%9C%93
Here is the source code of the class:
function TerminalReader() {
this._init.apply(this, arguments);
}
TerminalReader.prototype = {
_init: function(command, callback) {
this._callbackPipe = callback;
this._commandPipe = command;
this.idle = true;
this._childWatch = null;
},
executeReader: function() {
if(this.idle) {
this.idle = false;
try {
let [success, argv] = GLib.shell_parse_argv("sh -c '" + this._commandPipe + "'");
if(success) {
let [exit, pid, stdin, stdout, stderr] =
GLib.spawn_async_with_pipes(
null, // cwd
argv, // args
null, // env
GLib.SpawnFlags.SEARCH_PATH | GLib.SpawnFlags.DO_NOT_REAP_CHILD, //Use env path and no repet
null // child_setup
);
this._childPid = pid;
this._stdin = new Gio.UnixOutputStream({ fd: stdin, close_fd: true });
this._stdout = new Gio.UnixInputStream({ fd: stdout, close_fd: true });
this._stderr = new Gio.UnixInputStream({ fd: stderr, close_fd: true });
// We need this one too, even if don't actually care of what the process
// has to say on stderr, because otherwise the fd opened by g_spawn_async_with_pipes
// is kept open indefinitely
this._stderrStream = new Gio.DataInputStream({ base_stream: this._stderr });
this._dataStdout = new Gio.DataInputStream({ base_stream: this._stdout });
this._cancellableStderrStream = new Gio.Cancellable();
this._cancellableStdout = new Gio.Cancellable();
this.resOut = 1;
this._readStdout();
this.resErr = 1;
this._readStderror();
this._childWatch = GLib.child_watch_add(GLib.PRIORITY_DEFAULT, pid, Lang.bind(this, function(pid, status, requestObj) {
GLib.source_remove(this._childWatch);
this._childWatch = null;
this._stdin.close(null);
this.idle = true;
}));
}
//throw
} catch(err) {
if(err.code == GLib.SpawnError.G_SPAWN_ERROR_NOENT) {
err.message = _("Command not found.");
} else {
// The exception from gjs contains an error string like:
// Error invoking GLib.spawn_command_line_async: Failed to
// execute child process "foo" (No such file or directory)
// We are only interested in the part in the parentheses. (And
// we can't pattern match the text, since it gets localized.)
err.message = err.message.replace(/.*\((.+)\)/, '$1');
}
throw err;
}
}
},
destroy: function() {
try {
if(this._childWatch) {
GLib.source_remove(this._childWatch);
this._childWatch = null;
}
if(!this._dataStdout.is_closed()) {
this._cancellableStdout.cancel();
this._stdout.close_async(0, null, Lang.bind(this, this.closeStdout));
}
if(!this._stderrStream.is_closed()) {
this._cancellableStderrStream.cancel();
this._stderrStream.close_async(0, null, Lang.bind(this, this.closeStderrStream));
}
this._stdin.close(null);
this.idle = true;
}
catch(e) {
Main.notify("Error on close" + this._dataStdout.is_closed(), e.message);
}
},
closeStderrStream: function(std, result) {
try {
std.close_finish(result);
} catch(e) {
std.close_async(0, null, Lang.bind(this, this.closeStderrStream));
}
},
closeStdout: function(std, result) {
try {
std.close_finish(result);
} catch(e) {
std.close_async(0, null, Lang.bind(this, this.closeStderrStream));
}
},
_readStdout: function() {
this._dataStdout.fill_async(-1, GLib.PRIORITY_DEFAULT, this._cancellableStdout, Lang.bind(this, function(stream, result) {
try {
if(!this._dataStdout.is_closed()) {
if(this.resOut != -1)
this.resOut = this._dataStdout.fill_finish(result);// end of file
if(this.resOut == 0) {
let val = stream.peek_buffer().toString();
if(val != "")
this._callbackPipe(this._commandPipe, true, val);
this._stdout.close(this._cancellableStdout);
} else {
// Try to read more
this._dataStdout.set_buffer_size(2 * this._dataStdout.get_buffer_size());
this._readStdout();
}
}
} catch(e) {
global.log(e.toString());
}
}));
},
_readStderror: function() {
this._stderrStream.fill_async(-1, GLib.PRIORITY_DEFAULT, this._cancellableStderrStream, Lang.bind(this, function(stream, result) {
try {
if(!this._stderrStream.is_closed()) {
if(this.resErr != -1)
this.resErr = this._stderrStream.fill_finish(result);
if(this.resErr == 0) { // end of file
let val = stream.peek_buffer().toString();
if(val != "")
this._callbackPipe(this._commandPipe, false, val);
this._stderr.close(null);
} else {
this._stderrStream.set_buffer_size(2 * this._stderrStream.get_buffer_size());
this._readStderror();
}
}
} catch(e) {
global.log(e.toString());
}
}));
}
};
回答3:
calling spawn_async_with_pipes() isn't going to help you, as it gives you back an object with availlable pipes for stdin/stdout/stderr rather than giving you calls that are piped to one another.
Except for just calling a shell instance and letting it execute commands, the only way is to stick to the extension itself, letting GNOME handle everything using a temp file and default shell (one that overwrites itself if it already exists).
For the example code, lets do the same as journalctl | grep -i js would do on a CLI:
//Gio for File I/O and GLib for command execution
const Gio = imports.gi.Gio;
const GLib = imports.gi.GLib;
//Create an object for the temp file
let file = Gio.file_new_tmp(null);
//Now write the output of journalctl to the file
file[1].get_output_stream().write(GLib.spawn_command_line_sync("journalctl")[1], null);
//Execute the command and save the result, this locks the thread though,
//so don't use indefinite commands like journalctl -f
//This returns [Boolean success, String stdout, String stderr, Number exit_status]
let journalJS = GLib.spawn_command_line_sync('grep -i js ' + file[0].get_path())[1]
Now feel free to do with the data you have, as everything exits after the command is finished.
Don't forget to close the file using file[1].close(); and setting any remaining variables to null when finished.
来源：https://stackoverflow.com/questions/33911776/gnome-shell-extensions-how-to-run-a-command-with-pipes