On Aug 18, 2013, at 7:21 PM, // ravi <[email protected]> wrote:
> On Aug 18, 2013, at 5:52 PM, Mark Hahn <[email protected]> wrote:
>> When I run this bash script ...
>>
>> #!/bin/bash
>> tail -f log &
>> echo "tail is working" >> log
>>
>> it prints out "tail is working" as expected.
>>
>> My question is how can I do the same thing with a node command-line script?
>> I've tried everything but I can't come up with anything that works. Most of
>> my tries hang with the child_process never returning.
>>
>> By node command-line script I mean a file like this ...
>>
>> #!/usr/bin/env node
>> console.log "I'm a command-line script”
>>
>
> Are you expecting to see “tail is working” (or the equivalent) on the
> terminal? I am not entirely comfortable with Node’s child_process (in
> comparison to Unix fork/popen) but the documentation does say it is the
> equivalent of popen, so ‘stdout’ is not going to go to the terminal/tty
> (assuming you are using *nix).
>
> So, if you have:
>
> var spawn = require(‘child_process’).spawn,
> tail = spawn(‘tail’, [‘-f’, ‘log’]);
>
To fill that out, this skeletal version works pretty much just as the shell
script:
const LOGFILE = './tst.log';
var fs = require('fs'),
spawn = require('child_process').spawn,
tail = spawn('tail', ['-f', LOGFILE]);
var ctr = 0;
tail.stdout.on('data', function(data) { console.log(data.toString()); });
write_forever();
function write_forever()
{
fs.appendFileSync(LOGFILE, "test line " + ctr++);
setTimeout(write_forever, 2000);
}
—ravi
> Then, ostensibly(*) ‘tail.stdout’ will give you the stuff that is being added.
>
> I assume you are watching the file like this, using ’tail -f’, for some
> reason, rather than using some tail module.
>
> —ravi
>
>
> (*) I am speaking generally here since I do not know exactly how you are
> spawning the child and how the file content is being modified.
>
>>
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