std::filesystem::path::compare
std::filesystem::path::compare
|
(1) | (since C++17) |
|
(2) | (since C++17) |
|
(3) | (since C++17) |
Compares the lexical representations of the path and another path.
1) If root_name().native().compare(p.root_name().native())
is nonzero, returns that value.
Otherwise, if has_root_directory() != p.has_root_directory()
, returns a value less than zero if has_root_directory() is false
and a value greater than zero otherwise.
Otherwise returns a value less than, equal to or greater than 0 if the relative portion of the path (relative_path()) is respectively lexicographically less than, equal to or greater than the relative portion of p
(p.relative_path()
). Comparison is performed element-wise, as if by iterating both paths from begin() to end() and comparing the result of native() for each element.
2) Equivalent to compare(path(str))
.
3) Equivalent to compare(path(s))
.
Parameters
p | - | a path to compare to |
str | - | a string or string view representing path to compare to |
s | - | a null-terminated string representing path to compare to |
Return value
A value less than 0 if the path is lexicographically less than the given path.
A value equal to 0 if the path is lexicographically equal to the given path.
A value greater than 0 if the path is lexicographically greater than the given path.
Exceptions
2-3) (none)
Notes
For two-way comparisons, binary operators may be more suitable.
Example
#include <iostream>
#include <filesystem>
namespace fs = std::filesystem;
void demo(int rc, fs::path p1, fs::path p2) {
if(rc < 0) std::cout << p1 << " < " << p2 << '\n';
else if(rc > 0) std::cout << p1 << " > " << p2 << '\n';
else if(rc == 0) std::cout << p1 << "==" << p2 << '\n';
}
int main() {
fs::path p1 = "/a/b/"; // as if "a/b/." for lexicographical iteration
fs::path p2 = "/a/b/#";
demo(p1.compare(p2), p1, p2);
demo(p1.compare("a/b/_"), p1, "a/b/_");
}
Output:
"/a/b/" > "/a/b/#"
"/a/b/" < "a/b/_"
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 2936 | C++17 | compared all path elements directly | root name and root directory handled separately |
See also
lexicographically compares two paths (function) |
© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
http://en.cppreference.com/w/cpp/filesystem/path/compare