fstream get(char *，int)如何操作空行? [英] fstream get(char*, int) how to operate empty line?

问题描述

strfile.cpp中的代码:

code in strfile.cpp:

#include <fstream>
#include <iostream>
#include <assert.h>

#define SZ 100

using namespace std;

int main(){
char buf[SZ];
{
    ifstream in("strfile.cpp");
    assert(in);
    ofstream out("strfile.out");
    assert(out);
    int i = 1;

    while(!in.eof()){
        if(in.get(buf, SZ))
            int a = in.get();
        else{
            cout << buf << endl;
            out << i++ << ": " << buf << endl;
            continue;
        }
        cout << buf << endl;
        out << i++ << ": " << buf << endl;
    }
}
return 0;
}

我要操作所有文件 但在strfile.out中:

I want to operate all file but in strfile.out:

1: #include <fstream>
2: #include <iostream>
3: #include <assert.h>
4: ...(many empty line)

我知道fstream.getline(char *，int)这个函数可以管理它，但是我想知道如何做到这一点，只需使用函数"fstream.get()"即可.

I know that fstream.getline(char*, int) this function can manage it,but I want to know how to do this just use the function "fstream.get()".

推荐答案

由于ifstream::get(char*,streamsize)将在流上保留定界符(在本例中为\n)，因此您的调用永不进行，因此在您的调用程序中似乎您正在无休止地阅读空白行.

Because ifstream::get(char*,streamsize) will leave the delimiter (in this case \n) on the stream, your call never advances and thus it appears to your calling program that you are endlessly reading blank lines.

相反，您需要确定是否有换行符在流上等待，然后使用in.get()或in.ignore(1):

Instead you need to determine if a newline is waiting on the stream, and move past it using in.get() or in.ignore(1):

ifstream in("strfile.cpp");
ofstream out("strfile.out");

int i = 1;
out << i << ": ";

while (in.good()) {
    if (in.peek() == '\n') {
        // in.get(buf, SZ) won't read newlines
        in.get();
        out << endl << i++ << ": ";
    } else {
        in.get(buf, SZ);
        out << buf;      // we only output the buffer contents, no newline
    }
}

// output the hanging \n
out << endl;

in.close();
out.close();

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