Input Output

Node.io can be used to interact with files, databases or streams. By default, node.io reads from stdin (elements are separated by \n or \r\n) and writes to stdout.

Example 1: Stdin / stdout

csv_to_tsv.coffee

class CsvToTsv extends nodeio.JobClass
    run: (row) -> @emit row.replace ',' '\t'
    
@class = CsvToTsv
@job = new CsvToTsv()

Try it out

$ node.io csv_to_csv.coffee < input.csv > output.csv

Example 2: Files

Files can be read/written through stdin / stdout (see above), or specified inside the job.

csv_to_tsv.js

exports.job = new nodeio.Job({
    input: 'input.csv',
    run: function (row) {
        this.emit(row.replace(',', '\t'));
    }
    output: 'output.tsv',
});

The input or output files can be overridden at the command line

$ node.io -i new_input.csv -o new_output.tsv csv_to_tsv

Example 3: Databases & custom IO

To read rows from a database, use the following template. start begins at 0 and num is the number of rows to return. When there are no more rows, return false.

database_template.js

exports.job = new nodeio.Job({
    input: function (start, num, callback) {
        //
    },
    run: function (row) {
        this.emit(row);
    },
    output: function (rows) {
          //Note: this method always receives multiple rows as an array
          //
    },
});

Example 4: Streams

To read from read_stream and write to write_stream, use the following example

stream_template.js

exports.job = new nodeio.Job({
    input: function () {
        this.inputStream(read_stream);
        this.input.apply(this, arguments);
    },
    run: function (line) {
        this.emit(line);
    },
    output: function (lines) {
          write_stream.write(lines.join('\n'));
    },
});

Example 5: Reading files in a directory

node.io can be used to walk through all files in a directory, and optionally recurse through subdirectories.

walk_template.js

exports.job = new nodeio.Job({
    input: '/path/to/dir',
    run: function (full_path) {
        console.log(full_path);
        this.emit();
    }
});

recurse_template.js

exports.job = new nodeio.Job({recurse: true}, {
    input: '/path/to/dir',
    run: function (full_path) {
        console.log(full_path);
        this.emit();
    }
});

The input path can be overridden at the command line

$ node.io -i "/new/path" recurse_template