如何用ifstream读取文件信息保存到字符数组中

[jmghoul]

我想把一个txt文件中所有信息读取到char型数组中 现在不知道如何定义这个数组大小 如果定义固定大小的话文件太大又读取不全。有什么办法么

[东大坡居士]

全局定义大点

[东大坡居士]

or 先读文件大小。再动态申请

[jmghoul]

读取文件大小的函数有么？ 用new来申请数组大小么 char a = new char[?]

[nocodelife]

先获取文件的大小，然后动态申请

[ForestDB]

多看看标准库文档。 http://www.cplusplus.com/reference/istream/istream/seekg/

# include <iostream>
# include <fstream>
# include <ios>

using namespace std;

int main()
{
    ifstream in("y.cpp");
    in.seekg(0, ios::end);
    int length = in.tellg();
    in.seekg(0, ios::beg);
    char * buffer = new char[length];
    in.read(buffer, length);
    in.close();
    cout.write(buffer, length);
    delete [] buffer;

    return 0;
}

[ForestDB]

或者看看系统的api，比如Linux下的stat函数，也能得到文件的大小。

[AnYidan]

size_t fread(void *ptr, size_t size, size_t nobj, FILE *stream) fread reads from stream into the array ptr at most nobj objects of size size. fread returns the number of objects read; this may be less than the number requested. feof and ferror must be used to determine status. 如果返回值 等于 指定读出的数值，说明可能未读完

[Binzo]

new 动态内存分配。

[志士惜日短，愁人知夜长️]

引用 5 楼 ForestDB 的回复:

多看看标准库文档。
http://www.cplusplus.com/reference/istream/istream/seekg/

# include <iostream>
# include <fstream>
# include <ios>

using namespace std;

int main()
{
    ifstream in("y.cpp");
    in.seekg(0, ios::end);
    int length = in.tellg();
    in.seekg(0, ios::beg);
    char * buffer = new char[length];
    in.read(buffer, length);
    in.close();
    cout.write(buffer, length);
    delete [] buffer;

    return 0;
}

威武！