std::filesystem::is_symlink

 

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類
filesystem::path filesystem::filesystem_error filesystem::directory_entry filesystem::directory_iterator filesystem::recursive_directory_iterator    filesystem::file_status filesystem::space_info	filesystem::file_type filesystem::file_time_type filesystem::perms filesystem::perm_options filesystem::copy_options filesystem::directory_options
函式
filesystem::absolute filesystem::canonicalfilesystem::weakly_canonical filesystem::relativefilesystem::proximate filesystem::copy filesystem::copy_file filesystem::copy_symlink filesystem::create_directory filesystem::create_directories filesystem::create_hard_link filesystem::create_symlink filesystem::create_directory_symlink filesystem::current_path filesystem::temp_directory_path	filesystem::exists filesystem::equivalent filesystem::file_size filesystem::hard_link_count filesystem::last_write_time filesystem::permissions filesystem::read_symlink filesystem::remove filesystem::remove_all filesystem::rename filesystem::resize_file filesystem::space filesystem::status filesystem::symlink_status
檔案型別
filesystem::is_block_file filesystem::is_character_file filesystem::is_directory filesystem::is_empty filesystem::status_known	filesystem::is_fifo filesystem::is_other filesystem::is_regular_file filesystem::is_socket filesystem::is_symlink

 

定義於標頭檔案 <filesystem>
bool is_symlink( std::filesystem::file_status s ) noexcept;	(1)	(C++17 起)
bool is_symlink( const std::filesystem::path& p );	(2)	(C++17 起)
bool is_symlink( const std::filesystem::path& p, std::error_code& ec ) noexcept;	(3)	(C++17 起)

檢查給定檔案狀態或路徑是否對應於符號連結，如同由 POSIX S_IFLNK 確定一樣。

1) 等價於 s.type() == file_type::symlink。

2,3) 等價於 is_symlink(symlink_status(p)) 或 is_symlink(symlink_status(p, ec))。

引數

s	-	要檢查的檔案狀態
p	-	要檢查的路徑
ec	-	非丟擲過載中用於錯誤報告的出參

返回值

若由 p 指示的檔案或由 s 指示的型別指向符號連結則為 true。若發生錯誤，非丟擲過載返回 false。

異常

任何未標記為 noexcept 的過載都可能在記憶體分配失敗時丟擲 std::bad_alloc。

2,3) 若 OS API 呼叫失敗，則設定 std::error_code& 引數為 OS API 錯誤碼，若無錯誤則執行 ec.clear()。

示例

執行此程式碼

#include <cstdio>
#include <cstring>
#include <filesystem>
#include <fstream>
#include <iostream>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/un.h>
#include <unistd.h>
 
namespace fs = std::filesystem;
 
void demo_status(const fs::path& p, fs::file_status s)
{
    std::cout << p;
    // alternative: switch(s.type()) { case fs::file_type::regular: ...}
    if (fs::is_regular_file(s))
        std::cout << " is a regular file\n";
    if (fs::is_directory(s))
        std::cout << " is a directory\n";
    if (fs::is_block_file(s))
        std::cout << " is a block device\n";
    if (fs::is_character_file(s))
        std::cout << " is a character device\n";
    if (fs::is_fifo(s))
        std::cout << " is a named IPC pipe\n";
    if (fs::is_socket(s))
        std::cout << " is a named IPC socket\n";
    if (fs::is_symlink(s))
        std::cout << " is a symlink\n";
    if (!fs::exists(s))
        std::cout << " does not exist\n";
}
 
int main()
{
    // create files of different kinds
    fs::create_directory("sandbox");
    fs::create_directory("sandbox/dir");
    std::ofstream{"sandbox/file"}; // create regular file
    fs::create_symlink("file", "sandbox/symlink");
 
    mkfifo("sandbox/pipe", 0644);
    sockaddr_un addr;
    addr.sun_family = AF_UNIX;
    std::strcpy(addr.sun_path, "sandbox/sock");
    int fd = socket(PF_UNIX, SOCK_STREAM, 0);
    bind(fd, reinterpret_cast<sockaddr*>(&addr), sizeof addr);
 
    // demo different status accessors
    for (auto it{fs::directory_iterator("sandbox")}; it != fs::directory_iterator(); ++it)
        demo_status(*it, it->symlink_status()); // use cached status from directory entry
    demo_status("/dev/null", fs::status("/dev/null")); // direct calls to status
    demo_status("/dev/sda", fs::status("/dev/sda"));
    demo_status("sandbox/no", fs::status("/sandbox/no"));
 
    // cleanup (prefer std::unique_ptr-based custom deleters)
    close(fd);
    fs::remove_all("sandbox");
}

可能的輸出

"sandbox/file" is a regular file
"sandbox/dir" is a directory
"sandbox/pipe" is a named IPC pipe
"sandbox/sock" is a named IPC socket
"sandbox/symlink" is a symlink
"/dev/null" is a character device
"/dev/sda" is a block device
"sandbox/no" does not exist

參閱

statussymlink_status (C++17)(C++17)	確定檔案屬性 確定檔案屬性，檢查符號連結目標 (函式)
file_status (C++17)	表示檔案型別和許可權 (類)
status_known (C++17)	檢查檔案狀態是否已知 (函式)
is_block_file (C++17)	檢查給定路徑是否引用塊裝置 (函式)
is_character_file (C++17)	檢查給定路徑是否引用字元裝置 (函式)
is_directory (C++17)	檢查給定路徑是否引用目錄 (函式)
is_fifo (C++17)	檢查給定路徑是否引用命名管道 (函式)
is_other (C++17)	檢查引數是否引用“其他”檔案 (函式)
is_regular_file (C++17)	檢查引數是否引用常規檔案 (函式)
is_socket (C++17)	檢查引數是否引用命名 IPC 套接字 (函式)
exists (C++17)	檢查路徑是否引用現有檔案系統物件 (函式)
is_symlink	檢查目錄項是否指向符號連結 (std::filesystem::directory_entry 的公開成員函式)