fstream不解析路径 [英] fstream doesn't resolve path

问题描述

我是新的到c + +，并试图写一个简单的函数，将一个字符串保存到文件。
该函数工作，当我通过完整的路径到fstream，但它不解析相对路径。

这是我的代码的相关部分

  #include< iostream> 
 #include< fstream> 
 
 void writeToFile（）
 {
 std :: fstream fs; 
 fs.open（/home/blabla/Documents/test.txt，std :: fstream :: in | std :: fstream :: out | std :: fstream :: app）; 
 fs<< 测试内容; 
 
 fs.close（）; 
} 
  

这个工作正常，但我想在文件夹中创建文件，所以我试过这个

  fs.open（./test.txt，std :: fstream :: in | std :: fstream :: out | std :: fstream :: app）; 
  

我也试过了

  fs.open（〜/ Documents / test.txt，std :: fstream :: in | std :: fstream :: out | std :: fstream :: app）; 
  

他们都没有创建新文件，我没有得到任何错误信息。

我发现这个帖子，这表明，我可以传递相对路径到fstream，但只给出了窗口的例子。
fstream 的相对路径

我在Linux Mint上工作，目标环境是debian。

我非常感谢任何提示或建议，
Michael

$ b您的计划

  #include< iostream> ; 
 #include< fstream> 
 
 void writeToFile（）{
 std :: fstream fs; 
 fs.open（./test.txt，std :: fstream :: in | std :: fstream :: out | std :: fstream :: app）; 
 fs<< 测试内容; 
 
 fs.close（）; 
} 
 
 int main（）{
 writeToFile（）; 
} 
  

对我来说在 Coliru 。

正如你可以从 ls 输出，文件已创建

  a.out<可执行程序
 main.cpp<<源
 test.txt<<创建的文本文件
  

和 cat 转储文件的内容

 测试内容
  

如我在注释中提到的，〜/ Documents / test.txt 的路径由shell评估，而 ./ test.txt 如果你在同一个文件所在的目录下运行你的程序，应该可以使用现有的文件。

他们都没有创建新文件，我没有收到任何错误信息。

如果错误讯息 / openrel =nofollow> std :: fstream :: open（） 由于某种原因失败。

检查该调用之后的流状态，例如

  if（！fs）{std :: cerr< 无法打开文件<< std :: endl; } 
  

另一个选择是使用 std :: basic_ios :: exceptions（） std :: fstream（）的函数。

i am new to c++ and trying to write a simple function, that saves a string to a file. The function works, when i pass the full path to fstream, but it doesn't resolve relative paths.

Here is the relevant part of my code

#include <iostream>
#include <fstream>

void writeToFile ()
{
    std::fstream fs;
    fs.open ("/home/blabla/Documents/test.txt", std::fstream::in | std::fstream::out | std::fstream::app);
    fs << " test content";

    fs.close();
}

This works fine, but i would like to create the file in the folder, where my program is executed, so i tried this

fs.open ("./test.txt", std::fstream::in | std::fstream::out | std::fstream::app);

I also tried

fs.open ("~/Documents/test.txt", std::fstream::in | std::fstream::out | std::fstream::app);

Neither of them created a new file and i did not get any error message.

I found this post, which suggests, that i can pass relative paths to fstream but only gives windows examples. Relative path for fstream

I work on Linux Mint, the target environment is debian.

I am thankful for any hints or suggestions, Michael

解决方案

Your program

#include <iostream>
#include <fstream>

void writeToFile () {
    std::fstream fs;
    fs.open ("./test.txt", std::fstream::in | std::fstream::out | std::fstream::app);
    fs << " test content";

    fs.close();
}

int main() {
    writeToFile();
}

works perfectly fine for me on Coliru.

As you can see from the ls output, the file was created

a.out      << The executable program
main.cpp   << The source
test.txt   << The created text file

and cat at least dumps the content of the file

 test content

As mentioned in my comment, a path like ~/Documents/test.txt is evaluated by the shell, while ./test.txt should work for openting an existing file, if you're running your program in the same directory where the file exists.

"Neither of them created a new file and i did not get any error message."

You'll never get any kind of error message, if std::fstream::open() failed for some reason.
You have to check for the stream state after that call, like e.g.

 if(!fs) { std::cerr << "Could not open file" << std::endl; }

You may e.g. not have rights to create a file in this directory.

Another option is to use the std::basic_ios::exceptions() function of std::fstream(), to trigger an exception when the stream state runs into an error condition.

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