feat: add printenv command (#143)

README.md

@@ -724,6 +724,7 @@ Currently implemented (though not every option is supported):
 - [`touch`](https://man7.org/linux/man-pages/man1/touch.1.html) - Creates a file (note: flags have not been implemented yet).
 - [`unset`](https://man7.org/linux/man-pages/man1/unset.1p.html) - Unsets an environment variable.
 - [`cat`](https://man7.org/linux/man-pages/man1/cat.1.html) - Concatenate files and print on the standard output
+- [`printenv`](https://man7.org/linux/man-pages/man1/printenv.1.html) - Print all or part of environment
 - More to come. Will try to get a similar list as https://deno.land/manual/tools/task_runner#built-in-commands
 
 You can also register your own commands with the shell parser (see below).

mod.test.ts

@@ -3,6 +3,7 @@ import $, { build$, CommandBuilder, CommandContext, CommandHandler } from "./mod
 import {
   assert,
   assertEquals,
+  assertMatch,
   assertRejects,
   assertStringIncludes,
   assertThrows,
@@ -1463,3 +1464,32 @@ Deno.test("cat", async () => {
     }
   });
 });
+
+Deno.test("printenv", async () => {
+  {
+    const result = await $`printenv`.env("hello", "world").env("ab", "cd").text();
+    if (Deno.build.os === "windows") {
+      assertMatch(result, /HELLO=world/);
+      assertMatch(result, /AB=cd/);
+    } else {
+      assertMatch(result, /hello=world/);
+      assertMatch(result, /ab=cd/);
+    }
+  }
+  {
+    const result = await $`printenv hello ab`.env("hello", "world").env("ab", "cd").stdout("piped");
+    assertEquals(result.code, 0);
+    assertEquals(result.stdout, "world\ncd\n");
+  }
+  if (Deno.build.os === "windows") {
+    // windows is case insensitive
+    const result = await $`printenv HeLlO aB`.env("hello", "world").env("ab", "cd").stdout("piped");
+    assertEquals(result.code, 0);
+    assertEquals(result.stdout, "world\ncd\n");
+  }
+  {
+    const result = await $`printenv hello doesntExist`.env("hello", "world").env("ab", "cd").noThrow().stdout("piped");
+    assertEquals(result.code, 1);
+    assertEquals(result.stdout, "world\n");
+  }
+});

src/command.ts

@@ -1,5 +1,6 @@
 import { CommandHandler } from "./command_handler.ts";
 import { cdCommand } from "./commands/cd.ts";
+import { printEnvCommand } from "./commands/printenv.ts";
 import { cpCommand, mvCommand } from "./commands/cp_mv.ts";
 import { echoCommand } from "./commands/echo.ts";
 import { catCommand } from "./commands/cat.ts";
@@ -50,6 +51,7 @@ const textDecoder = new TextDecoder();
 
 const builtInCommands = {
   cd: cdCommand,
+  printenv: printEnvCommand,
   echo: echoCommand,
   cat: catCommand,
   exit: exitCommand,

src/command_handler.ts

@@ -14,6 +14,7 @@ export interface CommandPipeWriter extends Deno.WriterSync {
 export interface CommandContext {
   get args(): string[];
   get cwd(): string;
+  get env(): Record<string, string>;
   get stdin(): CommandPipeReader;
   get stdout(): CommandPipeWriter;
   get stderr(): CommandPipeWriter;

src/commands/printenv.ts

@@ -0,0 +1,47 @@
+import { CommandContext } from "../command_handler.ts";
+import { ExecuteResult, resultFromCode } from "../result.ts";
+
+export function printEnvCommand(context: CommandContext): ExecuteResult {
+  // windows expects env vars to be upcased
+  let args;
+  if (Deno.build.os === "windows") {
+    args = context.args.map((arg) => arg.toUpperCase());
+  } else {
+    args = context.args;
+  }
+
+  try {
+    const result = executePrintEnv(context.env, args);
+    context.stdout.writeLine(result);
+    if (args.some((arg) => context.env[arg] === undefined)) {
+      return resultFromCode(1);
+    }
+    return resultFromCode(0);
+  } catch (err) {
+    context.stderr.writeLine(`printenv: ${err?.message ?? err}`);
+    return resultFromCode(1);
+  }
+}
+
+/**
+ * follows printenv on linux:
+ * - if arguments are provided, return a string containing a list of all env variables as `repeat(KEY=VALUE\n)`
+ * - if no arguments are provided, return a string containing a list of the values of the provided env vars as `repeat(VALUE\n)`
+ */
+function executePrintEnv(env: Record<string, string>, args: string[]) {
+  const isWindows = Deno.build.os === "windows";
+  if (args.length === 0) {
+    return Object.entries(env)
+      // on windows, env vars are case insensitive
+      .map(([key, val]) => `${isWindows ? key.toUpperCase() : key}=${val}`)
+      .join("\n");
+  } else {
+    if (isWindows) {
+      args = args.map((arg) => arg.toUpperCase());
+    }
+    return Object.entries(env)
+      .filter(([key]) => args.includes(key))
+      .map(([_key, val]) => val)
+      .join("\n");
+  }
+}

src/deps.test.ts

@@ -3,6 +3,7 @@ import { createPathRef, PathRef } from "./path.ts";
 export {
   assert,
   assertEquals,
+  assertMatch,
   assertRejects,
   assertStringIncludes,
   assertThrows,

src/shell.ts

@@ -314,6 +314,9 @@ export class Context {
       get cwd() {
         return context.getCwd();
       },
+      get env() {
+        return context.getEnvVars();
+      },
       get stdin() {
         return context.stdin;
       },