std@0.139.0/examples/xeval.ts

Deno standard library
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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.import { parse } from "../flags/mod.ts";import { readStringDelim } from "../io/buffer.ts";
// See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/AsyncFunction.const AsyncFunction = Object.getPrototypeOf(async function () {}) .constructor;
const HELP_MSG = `xeval
Run a script for each new-line or otherwise delimited chunk of standard input.
Print all the usernames in /etc/passwd: cat /etc/passwd | deno run -A https://deno.land/std/examples/xeval.ts "a = $.split(':'); if (a) console.log(a[0])"
A complicated way to print the current git branch: git branch | deno run -A https://deno.land/std/examples/xeval.ts -I 'line' "if (line.startsWith('*')) console.log(line.slice(2))"
Demonstrates breaking the input up by space delimiter instead of by lines: cat LICENSE | deno run -A https://deno.land/std/examples/xeval.ts -d " " "if ($ === 'MIT') console.log('MIT licensed')",
USAGE: deno run -A https://deno.land/std/examples/xeval.ts [OPTIONS] <code>OPTIONS: -d, --delim <delim> Set delimiter, defaults to newline -I, --replvar <replvar> Set variable name to be used in eval, defaults to $ARGS: <code>`;
export type XevalFunc = (v: string) => void;
export interface XevalOptions { delimiter?: string;}
const DEFAULT_DELIMITER = "\n";
export async function xeval( reader: Deno.Reader, xevalFunc: XevalFunc, { delimiter = DEFAULT_DELIMITER }: XevalOptions = {},) { for await (const chunk of readStringDelim(reader, delimiter)) { // Ignore empty chunks. if (chunk.length > 0) { await xevalFunc(chunk); } }}
async function main() { const parsedArgs = parse(Deno.args, { boolean: ["help"], string: ["delim", "replvar"], alias: { delim: ["d"], replvar: ["I"], help: ["h"], }, default: { delim: DEFAULT_DELIMITER, replvar: "$", }, }); if (parsedArgs._.length != 1) { console.error(HELP_MSG); console.log(parsedArgs._); Deno.exit(1); } if (parsedArgs.help) { return console.log(HELP_MSG); }
const delimiter = parsedArgs.delim; const replVar = parsedArgs.replvar; const code = parsedArgs._[0];
// new AsyncFunction()'s error message for this particular case isn't great. if (!replVar.match(/^[_$A-z][_$A-z0-9]*$/)) { console.error(`Bad replvar identifier: "${replVar}"`); Deno.exit(1); }
const xEvalFunc = new AsyncFunction(replVar, code);
await xeval(Deno.stdin, xEvalFunc, { delimiter });}
if (import.meta.main) { main();}