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javascript - fs.readFile 未读取整个文件

问题描述

我不完全确定为什么，但是当我执行最终displayLogFile()函数时，该readFile()函数不会显示整个文件。目前，所有错误都使用此代码正确记录到 log.log 文件中。

这段代码只是故意出错的 4 个不同的函数。在每个函数 catch 块中，错误被写入文件。我希望displayLogFile()函数在写入所有错误后读取并显示此文件，但该readFile()函数并未显示整个文件。

var fs = require("fs");

var logStream = fs.createWriteStream("./log.log"); //routes errors to log.log file
var writeConsole = new console.Console(logStream, logStream);

//#5
const displayLogFile = () => { //should display log.log file after all writing has completed.
  console.log("This function is ran but readFileSync does not.");
    JSON.stringify(
    fs.readFile("./log.log", "utf-8", (err, file) => { 
      console.log(file); // This only console.log's: "Attempted to divide by zero." and is missing the other 3 logs from the file.
    })
  );
};

//#1
const divideByZero = () => { //testing error function
  if (1 / 0 === Infinity) throw "Attempted to divide by zero.";
};

//#2
const fileDoesNotExist = () => { //testing error function
  return fs.readFileSync("./NoFileNamedThis.txt", "utf-8");
};

//#3
const arrayOutOfBounds = () => { //testing error function
  const arr = ["", "", ""];
  if (arr[3] === undefined) throw "Index was outside the bounds of the array.";
};

//#4
const arrayIsNull = () => { //testing error function
  var arr = ["", "", ""];
  arr = null;
  return arr[0];
};

//all of these try/catches error out on purpose 

//#1
try { 
  divideByZero();
} catch (err) {
  writeConsole.error(err);
}

//#2
try {
  fileDoesNotExist();
} catch (err) {
  writeConsole.error(err);
}

//#3
try {
  arrayOutOfBounds();
} catch (err) {
  writeConsole.error(err);
}

//#4
try {
  arrayIsNull();
} catch (err) {
  writeConsole.error(err);
}

logStream.close();

//#5
displayLogFile(); // this should display all of the error messages that have been written to the log.log file.

这是 log.log 文件，它在所有函数编写过程中都被很好地填充：

Attempted to divide by zero. <-- ERROR #1
Error: ENOENT: no such file or directory, open <-- ERROR #2 './NoFileNamedThis.txt'
    at Object.openSync (fs.js:498:3)
    at Object.readFileSync (fs.js:394:35)
    at fileDoesNotExist (C:\Users:32:13)
    at Object.<anonymous> (C:\Users:53:3)
    at Module._compile (internal/modules/cjs/loader.js:1072:14)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1101:10)
    at Module.load (internal/modules/cjs/loader.js:937:32)
    at Function.Module._load (internal/modules/cjs/loader.js:778:12)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:76:12)
    at internal/main/run_main_module.js:17:47 {
  errno: -4058,
  syscall: 'open',
  code: 'ENOENT',
  path: './NoFileNamedThis.txt'
}
Index was outside the bounds of the array. <-- ERROR #3
TypeError: Cannot read property '0' of null <-- ERROR #4
    at arrayIsNull (C:\Users:43:13)
    at Object.<anonymous> (C:\Users:65:3)
    at Module._compile (internal/modules/cjs/loader.js:1072:14)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1101:10)
    at Module.load (internal/modules/cjs/loader.js:937:32)
    at Function.Module._load (internal/modules/cjs/loader.js:778:12)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:76:12)
    at internal/main/run_main_module.js:17:47

标签： javascriptreadfile

解决方案

问题可能是使用readFileSync，根据文档https://nodejs.org/api/fs.html#fs_fs_readfilesync_path_options，它不使用异步 readFile 之类的回调，它要么在当前堆栈中引发错误，要么返回文件内容。

因此，您可以更改readFileSync调用：

const file = fs.readFileSync("./log.log", "utf-8")
console.log(file)

或使用fs.readFile：

fs.readFile("./log.log", "utf-8", (err, data) => {
    if (err) throw err;
    console.log(data);
  });

正如@Pointy 在问题评论中指出的那样，在我的测试中，如果您在读取文件内容之前关闭 writeStream，它会起作用。我认为这个答案在fs.createWriteStream的行为中有更多细节

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