C++以只读方式打开文件
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/8255935/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
C++ open a file as read-only
提问by Dan1676
I have written a program which opens a file then displays line by line its contents (text file)
我写了一个程序，它打开一个文件，然后一行一行地显示它的内容（文本文件）
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main (int argc, char* argv[])
{
string STRING;
ifstream infile;
infile.open(argv[1]);
if (argc != 2)
{
cout << "ERROR.\n";
return 1;
}
if(infile.fail())
{
cout << "ERROR.\n";
return 1;
}
else
{
while(!infile.eof())
{
getline(infile,STRING);
cout<<STRING + "\n";
}
infile.close();
return 0;
}
}
What do I need to add to make the file be read only ?
我需要添加什么才能使文件只读？
(infile.open(argv[1])is where am guessing something goes)
（这infile.open(argv[1])是我猜测某事发生的地方）
回答by cnicutar
The class ifstreamis for reading only so, problem solved. Also, did you really mean to check argcafterusing argv[1]?
该课程ifstream仅供阅读，问题已解决。另外，你真的想argc在使用后检查argv[1]吗？
On the other hand, when you use fstreamyou need to specify how you want to open the file:
另一方面，当您使用时，fstream您需要指定打开文件的方式：
fstream f;
f.open("file", fstream::in | fstream::out); /* Read-write. */
回答by codaddict
The default modeparameter of openfor ifstreamclass is ios::in. That is
for class的默认模式参数是. 那是openifstreamios::in
infile.open(argv[1]);
is same as:
与：
infile.open(argv[1], ios::in);
So you are opening the file in read-only mode.
因此，您以只读模式打开文件。
回答by ybungalobill
You already open the file for read-only. Your can't write to it if you use ifstream. Even:
您已经以只读方式打开文件。如果您使用ifstream. 甚至：
infile.rdbuf()->sputc('a');
is guaranteed to fail.
保证失败。
回答by Christian
You don't need to do anything as the default value for the openmode is already ios_base::in. So you're already good to go :)
See here for more details: http://en.cppreference.com/w/cpp/io/basic_ifstream/open
您不需要做任何事情，因为 openmode 的默认值已经是ios_base::in。所以你已经很高兴了 :) 有关更多详细信息，请参见此处：http: //en.cppreference.com/w/cpp/io/basic_ifstream/open
