Reading lines or whole buffer from stdin (node.js)

Question

I am developing an interactive console interface in node.js which parses and compiles input. For this purpose I am using readline.question:

require('readline').question('> ', processCommandFunction)

Now the program should also be able to read input piped to stdin from the system shell, i.e.:

$ myprog < myfile.txt

It parses the input, but with readline.question it does so line by line. That breaks some input code which spans over separate lines.

I would like change the behavior of the program so that when used interactively, it processes line by line (like it currently does) but when a file is piped to it, it should process the whole file in one chunk. So I somehow need to check whether more data is coming after a linebreak. Can someone please point me in the right direction?

mscdex · Accepted Answer · 2015-02-18 14:27:12Z

4

You could check process.stdin.isTTY. If it is true, then use readline for your interactive mode. If it's not true, then just read data from process.stdin manually as a Readable stream.

Example:

if (process.stdin.isTTY) {
  // do readline stuff here
} else {
  var buf = '';
  process.stdin.on('data', function(d) {
    buf += d;
  }).on('end', function() {
    // do something with buffered text in `buf`
  }).setEncoding('utf8');
}

answered Feb 18, 2015 at 14:27

mscdex

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2 Comments

travelboy Over a year ago

Sounds good... but I just thought about what would happen if the user pastes a multi-line block of code into the console. Can I check if more incoming data is queued after the newline?

mscdex Over a year ago

Is it javascript code or ? If it's javascript, why not use a REPL instead?

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