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91 lines
2.6 KiB
TypeScript
91 lines
2.6 KiB
TypeScript
// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
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import { parse } from "../flags/mod.ts";
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import { readStringDelim } from "../io/bufio.ts";
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// See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/AsyncFunction.
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const AsyncFunction = Object.getPrototypeOf(async function (): Promise<void> {})
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.constructor;
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const HELP_MSG = `xeval
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Run a script for each new-line or otherwise delimited chunk of standard input.
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Print all the usernames in /etc/passwd:
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cat /etc/passwd | deno run -A https://deno.land/std/examples/xeval.ts "a = $.split(':'); if (a) console.log(a[0])"
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A complicated way to print the current git branch:
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git branch | deno run -A https://deno.land/std/examples/xeval.ts -I 'line' "if (line.startsWith('*')) console.log(line.slice(2))"
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Demonstrates breaking the input up by space delimiter instead of by lines:
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cat LICENSE | deno run -A https://deno.land/std/examples/xeval.ts -d " " "if ($ === 'MIT') console.log('MIT licensed')",
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USAGE:
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deno run -A https://deno.land/std/examples/xeval.ts [OPTIONS] <code>
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OPTIONS:
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-d, --delim <delim> Set delimiter, defaults to newline
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-I, --replvar <replvar> Set variable name to be used in eval, defaults to $
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ARGS:
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<code>`;
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export type XevalFunc = (v: string) => void;
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export interface XevalOptions {
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delimiter?: string;
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}
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const DEFAULT_DELIMITER = "\n";
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export async function xeval(
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reader: Deno.Reader,
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xevalFunc: XevalFunc,
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{ delimiter = DEFAULT_DELIMITER }: XevalOptions = {},
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): Promise<void> {
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for await (const chunk of readStringDelim(reader, delimiter)) {
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// Ignore empty chunks.
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if (chunk.length > 0) {
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await xevalFunc(chunk);
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}
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}
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}
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async function main(): Promise<void> {
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const parsedArgs = parse(Deno.args, {
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boolean: ["help"],
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string: ["delim", "replvar"],
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alias: {
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delim: ["d"],
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replvar: ["I"],
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help: ["h"],
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},
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default: {
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delim: DEFAULT_DELIMITER,
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replvar: "$",
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},
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});
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if (parsedArgs._.length != 1) {
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console.error(HELP_MSG);
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console.log(parsedArgs._);
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Deno.exit(1);
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}
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if (parsedArgs.help) {
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return console.log(HELP_MSG);
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}
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const delimiter = parsedArgs.delim;
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const replVar = parsedArgs.replvar;
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const code = parsedArgs._[0];
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// new AsyncFunction()'s error message for this particular case isn't great.
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if (!replVar.match(/^[_$A-z][_$A-z0-9]*$/)) {
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console.error(`Bad replvar identifier: "${replVar}"`);
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Deno.exit(1);
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}
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const xEvalFunc = new AsyncFunction(replVar, code);
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await xeval(Deno.stdin, xEvalFunc, { delimiter });
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}
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if (import.meta.main) {
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main();
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}
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