在 C++ 中将 2 个文本文件合并到第 3 个文本文件中

Question

我正在开发一个程序，该程序应该从 2 个不同的文本文件中获取一定范围的行并将它们合并到第三个文本文件中。我确信这非常简单，但我对 C++ 真的很陌生，不知道应该怎么做。我查看了几个示例，但它们都处理需要排序的输出文件，但我的不需要排序或类似的东西。

这两个文件如下所示：

prog2a.dat：

This is the first line
and this is the second line
and this is the third line
and the fourth
and the fifth
and here is the sixth and
this is the seventh with
the eighth following and the
ninth line here.
The tenth starts a new paragraph
with the eleventh and
the twelfth followed by the
thirteenth line, luck thirteenth
as well as the fourteenth
and the fifteenth and of course
the sixteenth and the
seventeenth.  Are there
any more, yes the eighteenth
and the nineteenth and finally the
twentieth.

prog2b.dat

This is the 1st line of many.
Here is the 2nd of several,
and the 3rd followed by
the 4th as well as the
5th which is the last in this paragraph
A new paragraph has the 6th, followed
by the 7th and
the 8th
and 9th closing with
the 10th.
For the next info the 11th will
lead followed by the 12th and
the 13th with the
14th not far behind and ending
with the 15th.
Finally the 16th
17th and
18th with the
19th and the
20th rounding out the document.

该程序应该从 prog2a 中获取第 5-15 行，从 prog2b 中获取第 4-12 行，并将它们合并到 outfile.dat 中。所以输出应该是这样的：

and the fifth
and here is the sixth and
this is the seventh with
the eighth following and the
ninth line here.
The tenth starts a new paragraph
with the eleventh and
the twelfth followed by the
thirteenth line, luck thirteenth
as well as the fourteenth
and the fifteenth and of course
the 4th as well as the
5th which is the last in this paragraph
A new paragraph has the 6th, followed
by the 7th and
the 8th
and 9th closing with
the 10th.
For the next info the 11th will
lead followed by the 12th and

这是我最近的代码：

#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;

int main() {
// Create output file
std::ofstream outFile("outfile.dat", ios::out);

// Open input file 1, if can't be opened, exit
std::ifstream in1("../prog2a.dat");
in1.open();
std::string line;
int count = 1;
    if(!in1) {
        cerr << "Open Failure" << endl;
        exit(1);
    } //end if
    else {
        while(std::getline(in1, line)) {
            if(count >= 5 && count <= 15) {
                outFile << line << "\n";
                ++count;
            }
        } //end while
    } //end else 
in1.close();

//Open input file 2, if can't be opened, exit
ifstream in2;
in2.open("../prog2b.dat");
    if(!in2) {
        cerr << "Open Failure" << endl;
        exit(1);
    } //end if
    else {
        while(std::getline(in2, line)) {
            if(count >= 4 && count <= 12) {
                outFile << line << "\n";
                ++count;
            }
        } //end while
    } //end else
in2.close();
} //end main

在编写代码时，当我尝试使用命令 ./prog2 运行程序时出现以下错误：

./prog2: line 1: /bin: is a directory
./prog2: line 2: Purpose:: command not found
./prog2: line 3: I/O:: No such file or directory
./prog2: line 4: Input:: command not found
./prog2: line 6: prog2a.dat:: command not found
./prog2: line 7: This: command not found
./prog2: line 8: and: command not found
./prog2: line 9: and: command not found
./prog2: line 10: and: command not found
./prog2: line 11: and: command not found
./prog2: line 12: and: command not found
./prog2: line 13: this: command not found
./prog2: line 14: the: command not found
./prog2: line 15: ninth: command not found
./prog2: line 16: The: command not found
./prog2: line 17: with: command not found
./prog2: line 18: the: command not found
./prog2: line 19: thirteenth: command not found
Assembler messages:
Error: can't open well for reading: No such file or directory
well:0: Error: can't open as for reading: No such file or directory
as:0: Error: can't open the for reading: No such file or directory
the:0: Error: can't open fourteenth for reading: No such file or directory
./prog2: line 21: and: command not found
./prog2: line 22: the: command not found
./prog2: line 23: seventeenth.: command not found
./prog2: line 24: any: command not found
./prog2: line 25: and: command not found
./prog2: line 26: twentieth.: command not found
./prog2: line 28: prog2b.dat:: command not found
./prog2: line 29: This: command not found
./prog2: line 30: Here: command not found
./prog2: line 31: and: command not found
./prog2: line 32: the: command not found
./prog2: line 33: 5th: command not found
./prog2: line 34: A: command not found
./prog2: line 35: by: command not found
./prog2: line 36: the: command not found
./prog2: line 37: and: command not found
./prog2: line 38: the: command not found
./prog2: line 39: For: command not found
./prog2: line 40: lead: command not found
./prog2: line 41: the: command not found
./prog2: line 42: 14th: command not found
./prog2: line 43: with: command not found
./prog2: line 44: Finally: command not found
./prog2: line 45: 17th: command not found
./prog2: line 46: 18th: command not found
./prog2: line 47: 19th: command not found
./prog2: line 48: 20th: command not found
./prog2: line 50: Output:: command not found
./prog2: line 52: backup/: is a directory
./prog2: line 57: using: command not found
./prog2: line 59: syntax error near unexpected token `('
./prog2: line 59: `int main() {'

我不知道发生了什么。我对 Unix 还是很陌生，所以这对我来说就像一堆乱码。不确定它是否重要，但我正在使用 g++ (GCC) 4.1.2 20080704 编译器在 Linux 环境中编写此程序。

就像我说的，我对此很陌生，因此非常感谢任何帮助。

Answer 1

以下是一些帮助您入门的示例：

复制所有内容：

std::ifstream in1("../prog2a.dat");

std::string line;

while(std::getline(in1, line)) // only loop when read succeeds
{
    // use line here
    outFile << line << '\n'; // copy line to output
}

跟踪行号：

std::ifstream in1("../prog2a.dat");

int count = 1; // line number count (starts at 1)
std::string line;

while(std::getline(in1, line)) // only loop when read succeeds
{
    // use line here
    outFile << line << '\n'; // copy line to output
    ++count; // keep track
}

那么你只需要弄清楚当行号 (count) 是你想要的时如何输出。

提示：永远不要在while() 循环中检查eof()。原因如下：http://www.parashift.com/c++-faq/istream-and-eof.html