smart-pipe

node-smart-pipe

Wrap STDIN buffers for programs that don't directly support stdin

Example

The following work cross-platform.

Asynchronous

var smartPipe = require('smart-pipe');
var exec = require('child_process').exec;
 
var buffer = new Buffer([1, 2, 3, 4]);
var piped = smartPipe(buffer);
 
var cmd = piped.command + 'xxd ' + piped.file;
 
var proc = exec(cmd, function(err, stdout, stderr) {
    console.log(stdout);
    piped.clean();
});
 
proc.stdin.write(piped.buffer);
proc.stdin.end();

Synchronous

var smartPipe = require('smart-pipe');
var exec = require('child_process').execSync;
 
var buffer = new Buffer([1, 2, 3, 4]);
var piped = smartPipe(buffer);
 
var cmd = piped.command + 'xxd ' + piped.file;
 
var result = exec(cmd, {input: piped.buffer});
console.log(result.toString());
piped.clean();

Explanation

You might be wondering, this seems really overkill.

• Why do I even need this module? Because different platforms handle piping differently. Some platforms (like Windows) don't handle it at all. This module identifies the correct way to pipe information to "stdin" through the use of file descriptors (file paths).
• Does this change the syntax of my commands? Slightly; you will need to use the filename version of the command. Whereas you would normally just pipe (i.e. echo hello | cat) you'll need to use the filename syntax (i.e. cat some_file.txt). This is because we pass the STDIN file descriptor as input.
• Does this work on windows? Sure does; On Windows, since there is only a quasi-STDIN at best, we write the buffer to a temporary file first and that becomes the filename.
• Why does this require a native injection on Linux? This issue explains a bit better, but essentially Node on Linux uses unix sockets to communicate with stdin of the child process instead of file descriptors. The native module handles this and performs small, cheap middleware operations upon opening the "file".
• What's up with prefixing my commands? As per the last question, this prefix will have the LD_PRELOAD information on Linux, and be completely blank on other platforms.
• Why do I need to call clean()? This is mainly on windows, but if a temporary file was written (on a platform that doesn't fully support STDIN), this will clean it. If you choose not to call .clean(), temporary files will be purged upon the exit of Node.

License

Licensed under the MIT License. You can find a copy of it in LICENSE.