C++ 如何从单独的字符串（安全地）构建完整路径字符串？
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How to build a full path string (safely) from separate strings?
提问by sas4740
Does C++ have any equivalent to python's function os.path.join? Basically, I'm looking for something that combines two (or more) parts of a file path so that you don't have to worry about making sure the two parts fit together perfectly. If it's in Qt, that would be cool too.
C++ 有什么等同于 python 的函数os.path.join吗？基本上，我正在寻找将文件路径的两个（或更多）部分组合在一起的东西，这样您就不必担心确保这两个部分完美地结合在一起。如果它在 Qt 中，那也会很酷。
Basically I spent an hour debugging some code and at least part of it was because root + filenamehad to be root/ + filename, and I'm looking to avoid that in the future.
基本上我花了一个小时调试一些代码，至少有一部分是因为root + filename必须是root/ + filename，我希望将来避免这种情况。
回答by
Only as part of Boost.Filesystemlibrary. Here is an example:
仅作为Boost.Filesystem库的一部分。下面是一个例子：
#include <iostream>
#include <boost/filesystem.hpp>
namespace fs = boost::filesystem;
int main ()
{
fs::path dir ("/tmp");
fs::path file ("foo.txt");
fs::path full_path = dir / file;
std::cout << full_path << std::endl;
return 0;
}
Here is an example of compiling and running (platform specific):
这是编译和运行的示例（特定于平台）：
$ g++ ./test.cpp -o test -lboost_filesystem -lboost_system
$ ./test
/tmp/foo.txt
回答by Shawn Blakesley
Similar to @user405725's answer (but not using boost), and mentioned by @ildjarnin a comment, this functionality is available as part of std::filesystem. The following code compiles using Homebrew GCC 9.2.0_1 and using the flag --std=c++17:
类似于@user405725的答案（但不使用 boost），并且@ildjarn在评论中提到，此功能可作为std::filesystem 的一部分使用。以下代码使用 Homebrew GCC 9.2.0_1 并使用标志编译--std=c++17：
#include <iostream>
#include <filesystem>
namespace fs = std::filesystem;
int main()
{
fs::path dir ("/tmp");
fs::path file ("foo.txt");
fs::path full_path = dir / file;
std::cout << full_path << std::endl;
return 0;
}
回答by frankc
At least in Unix / Linux, it's always safe to join parts of a path by /, even if some parts of the path already end in /, i.e. root/pathis equivalent to root//path.
至少在 Unix / Linux 中，/即使路径的某些部分已经以 结尾/，即root/path相当于root//path.
In this case, all you really need is to join things on /. That said, I agree with other answers that boost::filesystemis a good choice if it is available to you because it supports multiple platforms.
在这种情况下，您真正需要的只是加入/. 也就是说，我同意其他答案，boost::filesystem如果您可以使用它是一个不错的选择，因为它支持多个平台。
回答by LoSciamano
If you want to do this with Qt, you can use QFileInfoconstructor:
如果你想用 Qt 做到这一点，你可以使用QFileInfo构造函数：
QFileInfo fi( QDir("/tmp"), "file" );
QString path = fi.absoluteFilePath();
回答by kainjow
With C++11 and Qt you can do this:
使用 C++11 和 Qt，你可以这样做：
QString join(const QString& v) {
return v;
}
template<typename... Args>
QString join(const QString& first, Args... args) {
return QDir(first).filePath(join(args...));
}
Usage:
用法：
QString path = join("/tmp", "dir", "file"); // /tmp/dir/file
回答by Frank Osterfeld
In Qt, just use /in code when using Qt API (QFile, QFileInfo). It will do the right thing on all platforms. If you have to pass a path to a non-Qt function, or want to format it for displaying it to the user, use QDir:toNativeSeparators()e.g.:
在 Qt 中，/当使用 Qt API ( QFile, QFileInfo)时，只需在代码中使用。它会在所有平台上做正确的事情。如果您必须将路径传递给非 Qt 函数，或者想要对其进行格式化以将其显示给用户，请使用QDir:toNativeSeparators()例如：
QDir::toNativeSeparators( path );
It will replace /by the native equivalent (i.e. \on Windows). The other direction is done via QDir::fromNativeSeparators().
它将替换/为本地等效项（即\在 Windows 上）。另一个方向是通过QDir::fromNativeSeparators().
