In RingoJS there's a function called read
which allows you to read an entire stream until the end is reached. This is useful when you're making a command line application. For example you may write a tac
program as follows:
#!/usr/bin/env ringo
var string = system.stdin.read(); // read the entire input stream
var lines = string.split("\n"); // split the lines
lines.reverse(); // reverse the lines
var reversed = lines.join("\n"); // join the reversed lines
system.stdout.write(reversed); // write the reversed lines
This allows you to fire up a shell and run the tac
command. Then you type in as many lines as you wish to and after you're done you can press Ctrl + D (or Ctrl + Z on Windows) to signal the end of transmission .
I want to do the same thing in node.js but I can't find any function which would do so. I thought of using the readSync
function from the fs
library to simulate as follows, but to no avail:
fs.readSync(0, buffer, 0, buffer.length, null);
The file descriptor for stdin (the first argument) is 0
. So it should read the data from the keyboard. Instead it gives me the following error:
Error: ESPIPE, invalid seek
at Object.fs.readSync (fs.js:381:19)
at repl:1:4
at REPLServer.self.eval (repl.js:109:21)
at rli.on.self.bufferedCmd (repl.js:258:20)
at REPLServer.self.eval (repl.js:116:5)
at Interface.<anonymous> (repl.js:248:12)
at Interface.EventEmitter.emit (events.js:96:17)
at Interface._onLine (readline.js:200:10)
at Interface._line (readline.js:518:8)
at Interface._ttyWrite (readline.js:736:14)
How would you synchronously collect all the data in an input text stream and return it as a string in node.js? A code example would be very helpful.
As node.js is event and stream oriented there is no API to wait until end of stdin and buffer result, but it's easy to do manually
var content = '';
process.stdin.resume();
process.stdin.on('data', function(buf) { content += buf.toString(); });
process.stdin.on('end', function() {
// your code here
console.log(content.split('').reverse().join(''));
});
In most cases it's better not to buffer data and process incoming chunks as they arrive (using chain of already available stream parsers like xml or zlib or your own FSM parser)
The key is to use these two Stream events:
Event: 'data'
Event: 'end'
For stream.on('data', ...)
you should collect your data data into either a Buffer (if it is binary) or into a string.
For on('end', ...)
you should call a callback with you completed buffer, or if you can inline it and use return using a Promises library.
该特定任务有一个模块,称为concat-stream 。
Let me illustrate StreetStrider's answer.
Here is how to do it with concat-stream
var concat = require('concat-stream');
yourStream.pipe(concat(function(buf){
// buf is a Node Buffer instance which contains the entire data in stream
// if your stream sends textual data, use buf.toString() to get entire stream as string
var streamContent = buf.toString();
doSomething(streamContent);
}));
// error handling is still on stream
yourStream.on('error',function(err){
console.error(err);
});
Please note that process.stdin
is a stream.
If you are in async
context and have a recent version of Node.js, here is a quick suggestion :
const chunks = []
for await (let chunk of readable) {
chunks.push(chunk)
}
console.log(Buffer.concat(chunks))
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