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feat: add string/first
PR-URL: #989 Closes: #853 Co-authored-by: Athan Reines <kgryte@gmail.com> Co-authored-by: Philipp Burckhardt <pburckhardt@outlook.com> Reviewed-by: Athan Reines <kgryte@gmail.com> Reviewed-by: Philipp Burckhardt <pburckhardt@outlook.com>
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‎lib/node_modules/@stdlib/string/first/README.md‎

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<!--
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@license Apache-2.0
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Copyright (c) 2018 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# first
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> Return the first visual character(s) of a string.
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<section class="usage">
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## Usage
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```javascript
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var first = require( '@stdlib/string/first' );
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```
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#### first( str\[, n] )
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Returns the first visual character of a string.
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```javascript
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var out = first( 'last man standing' );
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// returns 'l'
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out = first( 'Hidden Treasures' );
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// returns 'H'
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```
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If provided a second argument, the function returns the first `n` characters.
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```javascript
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var out = first( 'foo bar', 5 );
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// returns 'foo b'
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out = first( 'foo bar', 10 );
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// returns 'foo bar'
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```
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</section>
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<!-- /.usage -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var first = require( '@stdlib/string/first' );
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var str = first( 'last man standing' );
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// returns 'l'
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str = first( 'presidential election' );
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// returns 'p'
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str = first( 'javaScript' );
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// returns 'j'
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str = first( 'Hidden Treasures' );
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// returns 'H'
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str = first( 'The Last of the Mohicans', 5 );
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// returns 'The L'
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str = first( '🐶🐮🐷🐰🐸', 2 );
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// returns '🐶🐮'
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str = first( '🐶🐮🐷🐰🐸', 10 );
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// returns '🐶🐮🐷🐰🐸'
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```
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</section>
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<!-- /.examples -->
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* * *
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<section class="cli">
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## CLI
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<section class="usage">
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### Usage
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```text
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Usage: first [options] [<string>]
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Options:
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-h, --help Print this message.
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-V, --version Print the package version.
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--n num Number of characters to return. Default: 1.
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--split sep Delimiter for stdin data. Default: '/\\r?\\n/'.
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```
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</section>
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<!-- /.usage -->
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<!-- CLI usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="notes">
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### Notes
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- If the split separator is a [regular expression][mdn-regexp], ensure that the `split` option is either properly escaped or enclosed in quotes.
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```bash
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# Not escaped...
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$ echo -n $'beep\nboop' | first --split /\r?\n/
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# Escaped...
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$ echo -n $'beep\nboop' | first --split /\\r?\\n/
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```
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- The implementation ignores trailing delimiters.
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</section>
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<!-- /.notes -->
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<section class="examples">
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### Examples
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```bash
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$ first beep
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b
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```
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To use as a [standard stream][standard-streams],
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```bash
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$ echo -n 'beep\nboop' | first --n=2
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be
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bo
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```
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By default, when used as a [standard stream][standard-streams], the implementation assumes newline-delimited data. To specify an alternative delimiter, set the `split` option.
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```bash
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$ echo -n 'beep\tboop' | first --split '\t'
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b
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b
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```
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</section>
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<!-- /.examples -->
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</section>
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<!-- /.cli -->
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<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
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<section class="related">
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</section>
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<!-- /.related -->
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<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="links">
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[standard-streams]: https://en.wikipedia.org/wiki/Standard_streams
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[mdn-regexp]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions
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</section>
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<!-- /.links -->

‎lib/node_modules/@stdlib/string/first/benchmark/benchmark.js‎

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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2021 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var bench = require( '@stdlib/bench' );
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var isString = require( '@stdlib/assert/is-string' ).isPrimitive;
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var pkg = require( './../package.json' ).name;
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var first = require( './../lib' );
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// MAIN //
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bench( pkg, function benchmark( b ) {
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var values;
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var out;
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var i;
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values = [
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'beep boop',
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'foo bar',
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'xyz abc'
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];
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b.tic();
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for ( i = 0; i < b.iterations; i++ ) {
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out = first( values[ i%values.length ] );
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if ( typeof out !== 'string' ) {
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b.fail( 'should return a string' );
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}
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}
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b.toc();
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if ( !isString( out ) ) {
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b.fail( 'should return a string' );
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}
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b.pass( 'benchmark finished' );
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b.end();
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});

‎lib/node_modules/@stdlib/string/first/bin/cli‎

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#!/usr/bin/env node
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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2018 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var resolve = require( 'path' ).resolve;
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var readFileSync = require( '@stdlib/fs/read-file' ).sync;
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var CLI = require( '@stdlib/cli/ctor' );
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var stdin = require( '@stdlib/process/read-stdin' );
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var stdinStream = require( '@stdlib/streams/node/stdin' );
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var RE_EOL = require( '@stdlib/regexp/eol' ).REGEXP;
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var isRegExpString = require( '@stdlib/assert/is-regexp-string' );
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var reFromString = require( '@stdlib/utils/regexp-from-string' );
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var first = require( './../lib' );
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// MAIN //
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/**
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* Main execution sequence.
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*
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* @private
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* @returns {void}
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*/
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function main() {
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var split;
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var flags;
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var args;
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var cli;
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var n;
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// Create a command-line interface:
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cli = new CLI({
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'pkg': require( './../package.json' ),
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'options': require( './../etc/cli_opts.json' ),
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'help': readFileSync( resolve( __dirname, '..', 'docs', 'usage.txt' ), {
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'encoding': 'utf8'
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})
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});
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// Get any provided command-line options:
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flags = cli.flags();
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if ( flags.help || flags.version ) {
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return;
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}
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if ( flags.n ) {
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n = parseInt( flags.n, 10 );
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} else {
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n = 1;
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}
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// Get any provided command-line arguments:
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args = cli.args();
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// Check if we are receiving data from `stdin`...
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if ( !stdinStream.isTTY ) {
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if ( flags.split ) {
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if ( !isRegExpString( flags.split ) ) {
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flags.split = '/'+flags.split+'/';
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}
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split = reFromString( flags.split );
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} else {
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split = RE_EOL;
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}
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return stdin( onRead );
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}
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console.log( first( args[ 0 ], n ) ); // eslint-disable-line no-console
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/**
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* Callback invoked upon reading from `stdin`.
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*
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* @private
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* @param {(Error|null)} error - error object
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* @param {Buffer} data - data
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* @returns {void}
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*/
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function onRead( error, data ) {
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var lines;
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var i;
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if ( error ) {
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return cli.error( error );
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}
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lines = data.toString().split( split );
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// Remove any trailing separators (e.g., trailing newline)...
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if ( lines[ lines.length-1 ] === '' ) {
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lines.pop();
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}
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for ( i = 0; i < lines.length; i++ ) {
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console.log( first( lines[ i ], n ) ); // eslint-disable-line no-console
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}
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}
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}
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main();

‎lib/node_modules/@stdlib/string/first/docs/repl.txt‎

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{{alias}}( str[, n] )
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Returns the first visual character(s) of a string.
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Parameters
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----------
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str: string
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Input string.
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n: integer (optional)
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Number of characters to return. Default: 1.
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Returns
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-------
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out: string
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Updated string.
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Examples
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--------
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> var out = {{alias}}( 'beep' )
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'b'
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> out = {{alias}}( 'Boop' )
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'B'
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> out = {{alias}}( 'foo bar', 5 )
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'foo b'
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See Also
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--------
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