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Showing content from https://en.cppreference.com/w/cpp/algorithm/../../cpp/symbol_index/../filesystem/canonical.html below:

std::filesystem::canonical, std::filesystem::weakly_canonical - cppreference.com

1,2)

Converts path

p

to a canonical absolute path, i.e. an absolute path that has no dot, dot-dot elements or symbolic links in its generic format representation. If

p

is not an absolute path, the function behaves as if it is first made absolute by

std::filesystem::absolute(p)

. The path

p

must exist.

3,4)

Returns a path composed by

operator/=

from the result of calling

canonical()

with a path argument composed of the leading elements of

p

that exist (as determined by

status(p)

status(p, ec)

), if any, followed by the elements of

p

that do not exist. The resulting path is in

normal form

[edit] Parameters p - a path which may be absolute or relative; for canonical it must be an existing path ec - error code to store error status to [edit] Return value

3,4) 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

Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails.

1,3)

Throws

std::filesystem::filesystem_error

on underlying OS API errors, constructed with

p

as the first path argument and the OS error code as the error code argument.

2,4)

Sets a

std::error_code&

parameter to the OS API error code if an OS API call fails, and executes

ec.clear()

if no errors occur.

[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

Possible output:

Current path is "/tmp/a/b/c1/d"
Canonical path for "../../c2/./e" is "/tmp/a/b/c2/e"
Weakly canonical path for "../no-such-file" is "/tmp/a/b/c1/no-such-file"
Canonical path for "../no-such-file" threw exception:
filesystem error: in canonical: No such file or directory [../no-such-file] [/tmp/a/b/c1/d]
Deleted 6 files or directories.

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior LWG 2956 C++17 canonical has a spurious base parameter removed [edit] See also

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