std::filesystem::is_block_file

STD：：文件系统：：is[医]块[医]档案

Defined in header
bool is_block_file( std::filesystem::file_status s	(1)	(since C++17)
bool is_block_file( const std::filesystem::path& p bool is_block_file( const std::filesystem::path& p, std::error_code& ec	(2)	(since C++17)

检查给定的文件状态或路径是否与块特殊文件相对应，就像由POSIX确定的那样。斯[医]ISBLK块特殊文件的示例是块设备，如/dev/sda或/dev/loop0在Linux上。

1%29相当于s.type() == file_type::block...

2%29相当于is_block_file(status(p))或is_block_file(status(p, ec))...

参数

s	-	file status to check
p	-	path to examine
ec	-	out-parameter for error reporting in the non-throwing overload

返回值

true如果由p或者如果所指示的类型s指的是块设备。非抛出重载返回。false如果发生错误。

例外

1%29

noexcept规格：

noexcept

2，3%29不需要std::error_code&参数抛文件系统[医]误差关于基础OS API错误，使用p作为第一个参数和操作系统错误代码作为错误代码参数。std::bad_alloc如果内存分配失败，则可能引发。过载std::error_code&参数，如果OSAPI调用失败，则将其设置为OSAPI错误代码，并执行ec.clear()如果没有错误发生。这个过载

noexcept规格：

noexcept

例

二次

#include <iostream>
#include <fstream>
#include <cstdio>
#include <cstring>
#include <filesystem>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/stat.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"
    std::ofstream("sandbox/file" // create regular file
    fs::create_directory("sandbox/dir"
    mkfifo("sandbox/pipe", 0644
    struct 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, (struct sockaddr*)&addr, sizeof addr
    fs::create_symlink("file", "sandbox/symlink"
 
    // 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
    close(fd
    fs::remove_all("sandbox"
}

二次

可能的产出：

二次

"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

二次

另见

statussymlink_status (C++17)(C++17)	determines file attributesdetermines file attributes, checking the symlink target (function)
file_status (C++17)	represents file type and permissions (class)
status_known (C++17)	checks whether file status is known (function)
is_character_file (C++17)	checks whether the given path refers to a character device (function)
is_directory (C++17)	checks whether the given path refers to a directory (function)
is_fifo (C++17)	checks whether the given path refers to a named pipe (function)
is_other (C++17)	checks whether the argument refers to an other file (function)
is_regular_file (C++17)	checks whether the argument refers to a regular file (function)
is_socket (C++17)	checks whether the argument refers to a named IPC socket (function)
is_symlink (C++17)	checks whether the argument refers to a symbolic link (function)
exists (C++17)	checks whether path refers to existing file system object (function)
statussymlink_status	status of the file designated by this directory entrysymlink_status of the file designated by this directory entry (public member function of std::filesystem::directory_entry)

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