std::filesystem::path::compare
From cppreference.com
< cpp | filesystem | path
int compare( const path& p ) const noexcept; |
(1) | (since C++17) |
int compare( const string_type& str ) const; int compare( std::basic_string_view<value_type> str ) const; |
(2) | (since C++17) |
int compare( const value_type* s ) const; |
(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
Run this code
#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) |