118 lines
2.6 KiB
Markdown
118 lines
2.6 KiB
Markdown
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# outpipe
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write output to a file through shell commands
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# purpose
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Suppose you have a tool like
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[watchify](https://npmjs.com/package/watchify)
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or [factor-bundle](https://npmjs.com/package/factor-bundle)
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that write to multiple files or write to the same file more than once.
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If you want to pipe the output of these tools to other programs, such as
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minification with the `uglify` command, it's very difficult! You might need to
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use the tool's API or use a separate command to watch for changes to the output
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files. Ick.
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You don't get the elegance of something like:
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``` sh
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$ browserify main.js | uglifyjs -cm | gzip > bundle.js.gz
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```
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Until now! With this library and a hypothetical version of watchify, you could
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do:
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``` sh
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$ watchify main.js -dv -o 'uglifyjs -cm | gzip > bundle.js.gz'
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```
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# example
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Here's a small watcher program that will just copy input files to a destination,
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but transforms can be applied along the way with shell pipes and redirects.
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``` js
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var outpipe = require('outpipe');
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var gaze = require('gaze');
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var fs = require('fs');
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var minimist = require('minimist');
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var argv = minimist(process.argv.slice(2), {
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alias: { o: 'output' }
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});
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var file = argv._[0];
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gaze(file, function (err, w) {
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w.on('changed', read);
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});
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read();
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function read () {
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var r = fs.createReadStream(file);
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r.pipe(outpipe(argv.output));
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}
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```
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We can run the program with a single output file:
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``` sh
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$ node watch.js input/x.js -o output/hmm.js
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```
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which just copies `x.js` to `output/hmm.js` whenever `x.js` changes.
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We could also run a minification step using the `uglify` command:
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``` sh
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$ node watch.js input/x.js -o 'uglifyjs -cm > output/wow.js'
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```
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or we can just print the size of the minified and gzipped output to stdout:
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``` sh
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$ node watch.js input/x.js -o 'uglifyjs -cm | gzip | wc -c'
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123
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```
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or we could write that size to a file:
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``` sh
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$ node watch.js input/x.js -o 'uglifyjs -cm | gzip | wc -c > size.txt'
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```
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# methods
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``` js
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var outpipe = require('outpipe')
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```
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## var w = outpipe(cmd, opts={})
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Return a writable stream `w` that will pipe output to the command string `cmd`.
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If `cmd` has no operators (`|` or `>`), it will write to a file.
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Otherwise, each command between pipes will be executed and output is written to
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a file if `>` is given.
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`opts` can be:
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* `opts.env` - an object mapping environment variables to their values or a
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`function (key) {}` that returns the values.
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stdout and stderr are forwarded to process.stdout and process.stderr if
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unhandled in the command.
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# install
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With [npm](https://npmjs.org) do:
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```
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npm install outpipe
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```
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# license
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MIT
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