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std::filesy...:is_symlink(3) C++ Standard Libary std::filesy...:is_symlink(3) NAME std::filesystem::directory_entry::is_symlink - std::filesystem::direc- tory_entry::is_symlink Synopsis bool is_symlink() const; (since C++17) bool is_symlink( std::error_code& ec ) const noexcept; Checks whether the pointed-to object is a symlink. Effectively re- turns std::filesystem::is_symlink(symlink_status()) or std::filesystem::is_symlink(symlink_status(ec)), respectively. Parameters ec - out-parameter for error reporting in the non-throwing overload Return value true if the referred-to filesystem object is a symlink, false other- wise. Exceptions The overload that does not take a std::error_code& parameter throws filesystem::filesystem_error on underlying OS API errors, con- structed with p as the first path argument and the OS error code as the error code argu- ment. 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. Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails. Example // Run this code #include <cstdio> #include <cstring> #include <filesystem> #include <fstream> #include <functional> #include <iostream> #include <memory> #include <sys/socket.h> #include <sys/stat.h> #include <sys/un.h> #include <unistd.h> namespace fs = std::filesystem; void print_entry_type(std::filesystem::directory_entry const& entry) { std::cout << entry.path() << ": "; if (!entry.exists()) std::cout << "does not exist "; if (entry.is_block_file()) std::cout << "is a block device "; if (entry.is_character_file()) std::cout << "is a character device "; if (entry.is_directory()) std::cout << "is a directory "; if (entry.is_fifo()) std::cout << "is a named IPC pipe "; if (entry.is_regular_file()) std::cout << "is a regular file "; if (entry.is_socket()) std::cout << "is a named IPC socket "; if (entry.is_symlink()) std::cout << "(a symlink) "; if (entry.is_other()) std::cout << "(an `other` file) "; std::cout <<'\n'; } template <typename Type, typename Fun> class scoped_cleanup { std::unique_ptr<Type, std::function<void(const Type*)>> u; public: scoped_cleanup(Type* ptr, Fun fun) : u{ptr, std::move(fun)} {} }; int main() { // create files of different kinds std::filesystem::current_path(fs::temp_directory_path()); const std::filesystem::path sandbox{"sandbox"}; scoped_cleanup remove_all_at_exit{&sandbox, [](const fs::path* p) { std::cout << "cleanup: remove_all(" << *p << ")\n"; fs::remove_all(*p); } }; std::filesystem::create_directory(sandbox); std::ofstream{sandbox/"file"}; // creates a regular file std::filesystem::create_directory(sandbox/"dir"); mkfifo((sandbox/"pipe").string().data(), 0644); struct sockaddr_un addr; addr.sun_family = AF_UNIX; std::strcpy(addr.sun_path, (sandbox/"sock").string().data()); int fd {socket(PF_UNIX, SOCK_STREAM, 0)}; scoped_cleanup close_socket_at_exit{&fd, [](const int* f) { std::cout << "cleanup: close socket #" << *f << '\n'; close(*f); } }; bind(fd, reinterpret_cast<sockaddr*>(std::addressof(addr)), sizeof addr); fs::create_symlink("file", sandbox/"symlink"); for (std::filesystem::directory_entry entry: fs::directory_itera- tor(sandbox)) { print_entry_type(entry); } // direct calls to status: for (const char* str: {"/dev/null", "/dev/cpu", "/usr/in- clude/c++", "/usr/include/asm", "/usr/include/time.h"}) { print_entry_type(fs::directory_entry{str}); } } // cleanup via `scoped_cleanup` objects Possible output: "sandbox/symlink": is a regular file (a symlink) "sandbox/sock": is a named IPC socket (an `other` file) "sandbox/pipe": is a named IPC pipe (an `other` file) "sandbox/dir": is a directory "sandbox/file": is a regular file "/dev/null": is a character device (an `other` file) "/dev/cpu": does not exist "/usr/include/c++": is a directory "/usr/include/asm": is a directory (a symlink) "/usr/include/time.h": is a regular file cleanup: close socket #3 cleanup: remove_all("sandbox") See also is_symlink checks whether the argument refers to a symbolic link (C++17) (function) http://cppreference.com 2022.07.31 std::filesy...:is_symlink(3)
NAME | Synopsis | Parameters | Return value | Exceptions | Example | Possible output: | See also
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