Question

我正在连续地将字符串值写入文本文件

std::string line =('8101001033900039','00','22','','','','','3','','0'),

这个字符串我们正在写一个文本文件，如下面的

outfile.open((char*)fileName.c_str(), ios::app);



if(outfile.is_open())
    {
        // write inputted data into the file.
        DBGF_TRACE("3.write line : %s", line);
        outfile<< line << std::endl;
        DBGF_TRACE("write line : %s", line);
    }

现在我得到的错误是，有时它的写入失败了。有人可以帮忙吗

Answer 1

首先是什么：

std::string line =('8101001033900039','00','22','','','','','3','','0');

编译器应该给你这样的东西：

prog.cc:8:24: warning: character constant too long for its type
     std::string line =('8101001033900039','00','22','','','','','3','','0');
                        ^~~~~~~~~~~~~~~~~~
prog.cc:8:43: warning: multi-character character constant [-Wmultichar]
     std::string line =('8101001033900039','00','22','','','','','3','','0');
                                           ^~~~
prog.cc:8:48: warning: multi-character character constant [-Wmultichar]
     std::string line =('8101001033900039','00','22','','','','','3','','0');
                                                ^~~~
prog.cc:8:53: error: empty character constant
     std::string line =('8101001033900039','00','22','','','','','3','','0');
                                                     ^~
prog.cc:8:56: error: empty character constant
     std::string line =('8101001033900039','00','22','','','','','3','','0');
                                                        ^~
prog.cc:8:59: error: empty character constant
     std::string line =('8101001033900039','00','22','','','','','3','','0');
                                                           ^~
prog.cc:8:62: error: empty character constant
     std::string line =('8101001033900039','00','22','','','','','3','','0');
                                                              ^~
prog.cc:8:69: error: empty character constant
     std::string line =('8101001033900039','00','22','','','','','3','','0');
                                                                     ^~
prog.cc: In function 'int main()':
prog.cc:8:43: warning: left operand of comma operator has no effect [-Wunused-value]
     std::string line =('8101001033900039','00','22','','','','','3','','0');
                                           ^~~~
prog.cc:8:48: warning: right operand of comma operator has no effect [-Wunused-value]
     std::string line =('8101001033900039','00','22','','','','','3','','0');
                                                ^~~~
prog.cc:8:53: warning: right operand of comma operator has no effect [-Wunused-value]
     std::string line =('8101001033900039','00','22','','','','','3','','0');
                                                     ^~
prog.cc:8:56: warning: right operand of comma operator has no effect [-Wunused-value]
     std::string line =('8101001033900039','00','22','','','','','3','','0');
                                                        ^~
prog.cc:8:59: warning: right operand of comma operator has no effect [-Wunused-value]
     std::string line =('8101001033900039','00','22','','','','','3','','0');
                                                           ^~
prog.cc:8:62: warning: right operand of comma operator has no effect [-Wunused-value]
     std::string line =('8101001033900039','00','22','','','','','3','','0');
                                                              ^~
prog.cc:8:65: warning: right operand of comma operator has no effect [-Wunused-value]
     std::string line =('8101001033900039','00','22','','','','','3','','0');
                                                                 ^~~
prog.cc:8:69: warning: right operand of comma operator has no effect [-Wunused-value]
     std::string line =('8101001033900039','00','22','','','','','3','','0');
                                                                     ^~
prog.cc:8:72: warning: right operand of comma operator has no effect [-Wunused-value]
     std::string line =('8101001033900039','00','22','','','','','3','','0');
                                                                        ^~~
prog.cc:8:71: error: conversion from 'char' to non-scalar type 'std::__cxx11::string' {aka 'std::__cxx11::basic_string<char>'} requested
     std::string line =('8101001033900039','00','22','','','','','3','','0');
                       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~

因此数据本身并不正常。

现在，让我们用双引号替换单引号，因为你可能想要字符串，如下所示：

std::string line =("8101001033900039","00","22","","","","","3","","0");

然后只将最右边的操作数分配给line，这意味着line现在等于"0"。在What does i = (i, ++i, 1) + 1; do?

中详细了解相关信息

编辑：

你需要这个：

#include <fstream>
#include <string>
#include <iostream>

int main(void) {
    std::string fileName = "output.txt";
    std::string line ="('8101001033900039','00','22','','','','','3','','0'),"; 
    std::ofstream out(fileName.c_str());
    out << line << std::endl;
    out.close();
    return 0;
}

有时在写入文本文件时遇到错误

1 个答案: