std::filesystem::canonical, std::filesystem::weakly_canonical
From cppreference.com
< cpp | filesystem
| Defined in header <filesystem>
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| path canonical( const std::filesystem::path& p, const std::filesystem::path& base = std::filesystem::current_path() ); |
(1) | (since C++17) |
| path canonical( const std::filesystem::path& p, std::error_code& ec ); |
(2) | (since C++17) |
| path canonical( const std::filesystem::path& p, const std::filesystem::path& base, |
(3) | (since C++17) |
| path weakly_canonical(const std::filesystem::path& p); |
(4) | (since C++17) |
| path weakly_canonical(const std::filesystem::path& p, std::error_code& ec); |
(5) | (since C++17) |
1-3) Converts path
p to a canonical absolute path, i.e. an absolute path that has no dot, dot-dot elements or symbolic links. If p is not an absolute path, the function behaves as if it is first made absolute by absolute(p, base) or absolute(p) for (2). The path p must exist.4-5) Returns a path composed by
operator/= from the result of calling canonical() without a base argument and with a path argument composed of the leading elements of p that exist (as determined by status(p) or status(p, ec)), if any, followed by the elements of p that do not exist, if any. The resulting path is in normal form.Contents |
[edit] Parameters
| p | - | a path which may be absolute or relative to base, and which must be an existing path
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| base | - | base path to be used in case p is relative
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| ec | - | error code to store error status to |
[edit] Return value
1-3) An absolute path that resolves to the same file as absolute(p, base) (or absolute(p) for (2)).
4-5) A normal path of the form
canonical(x)/y, where x is a path composed of the longest leading sequence of elements in p that exist, and y is a path composed of the remaining trailing non-existent elements of p[edit] Exceptions
The overload that does not take a std::error_code& parameter throws filesystem_error on underlying OS API errors, constructed withp as the first argument, base as the second argument, and the OS error code as the error code argument. std::bad_alloc may be thrown if memory allocation fails. The overload taking a std::error_code& parameter sets it to the OS API error code if an OS API call fails, and executes ec.clear() if no errors occur. This overload has noexcept specification:
noexcept
[edit] Notes
The function canonical() is modeled after the POSIX realpath.
The function weakly_canonical() was introduced to simplify operational semantics of relative().
[edit] Example
Run this code
#include <iostream> #include <filesystem> namespace fs = std::filesystem; int main() { fs::path p = fs::path("..") / ".." / "AppData"; std::cout << "Current path is " << fs::current_path() << '\n' << "Canonical path for " << p << " is " << canonical(p) << '\n'; }
Possible output:
Current path is "C:\Users\abcdef\AppData\Local\Temp" Canonical path for "..\..\AppData" is "C:/Users\abcdef\AppData"
[edit] See also
| (C++17) |
represents a path (class) |
| (C++17)(C++17) |
composes an absolute path converts a path to an absolute path replicating OS-specific behavior (function) |
| (C++17) |
composes a relative path (function) |