1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
|
import { parse } from "../flags/mod.ts";
import { readStringDelim } from "../io/bufio.ts";
/* eslint-disable-next-line max-len */
// See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/AsyncFunction.
const AsyncFunction = Object.getPrototypeOf(async function (): Promise<void> {})
.constructor;
/* eslint-disable max-len */
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>`;
/* eslint-enable max-len */
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 = {}
): Promise<void> {
for await (const chunk of readStringDelim(reader, delimiter)) {
// Ignore empty chunks.
if (chunk.length > 0) {
await xevalFunc(chunk);
}
}
}
async function main(): Promise<void> {
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();
}
|
