C++ fstream 不会创建文件
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fstream won't create a file
提问by raphnguyen
I'm simply trying to create a text file if it does not exist and I can't seem to get fstreamto do this.
我只是想创建一个文本文件，如果它不存在，我似乎fstream无法做到这一点。
#include <fstream>
using std::fstream;
int main(int argc, char *argv[]) {
fstream file;
file.open("test.txt");
file << "test";
file.close();
}
Do I need to specify anything in the open()function in order to get it to create the file? I've read that you can't specify ios::inas that will expect an already existing file to be there, but I'm unsure if other parameters need to be specified for a file that does not already exist.
我是否需要在open()函数中指定任何内容才能让它创建文件？我已经读到您不能指定，ios::in因为这会期望已经存在的文件存在，但我不确定是否需要为尚不存在的文件指定其他参数。
采纳答案by haitaka
You should add fstream::out to open method like this:
您应该将 fstream::out 添加到 open 方法中，如下所示：
file.open("test.txt",fstream::out);
More information about fstream flags, check out this link: http://www.cplusplus.com/reference/fstream/fstream/open/
有关 fstream 标志的更多信息，请查看此链接：http: //www.cplusplus.com/reference/fstream/fstream/open/
回答by ceruleus
You need to add some arguments. Also, instancing and opening can be put in one line:
您需要添加一些参数。此外，实例化和打开可以放在一行中：
fstream file("test.txt", fstream::in | fstream::out | fstream::trunc);
回答by Ritesh Kumar Gupta
This will do:
这将：
#include <fstream>
#include <iostream>
using std::fstream;
int main(int argc, char *argv[]) {
fstream file;
file.open("test.txt",std::ios::out);
file << fflush;
file.close();
}
