C++ – Determining if directory (not a file) exists in Linux [duplicate]
How would I determine if a directory (not a file) existed using C++ in Linux? I tried using the stat() function but it returned positive when a file was found. I only want to find if the inputted string is a directory, not something else.
6 Answers 6
According to man(2) stat you can use the S_ISDIR macro on the st_mode field:
Side note, I would recommend using Boost and/or Qt4 to make cross-platform support easier if your software can be viable on other OSs.
how about something i found here
If you can check out the boost filesystem library. It’s a great way to deal with this kind of problems in a generic and portable manner.
In this case it would suffice to use:
The way I understand your question is this: you have a path, say, /foo/bar/baz (baz is a file) and you want to know whether /foo/bar exists. If so, the solution looks something like this (untested):
In C++17**, std::filesystem provides two variants to determine the existence of a path:
- is_directory() determines, if a path is a directory and does exist in the actual filesystem
- exists() just determines, if the path exists in the actual filesystem (not checking, if it is a directory)
Example (without error handling):
Both functions throw filesystem_error in case of errors. If you want to avoid catching exceptions, use the overloaded variants with std::error_code as second parameter.
If you want to find out whether a directory exists because you want to do something with it if it does (create a file/directory inside, scan its contents, etc) you should just go ahead and do whatever you want to do, then check whether it failed, and if so, report strerror(errno) to the user. This is a general principle of programming under Unix: don’t try to figure out whether the thing you want to do will work. Attempt it, then see if it failed.
If you want to behave specially if whatever-it-was failed because a directory didn’t exist (for instance, if you want to create a file and all necessary containing directories) you check for errno == ENOENT after open fails.
I see that one responder has recommended the use of boost::filesystem . I would like to endorse this recommendation, but sadly I cannot, because boost::filesystem is not header-only, and all of Boost’s non-header-only modules have a horrible track record of causing mysterious breakage if you upgrade the shared library without recompiling the app, or even if you just didn’t manage to compile your app with exactly the same flags used to compile the shared library. The maintenance grief is just not worth it.
C file exists linux
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