肇庆软件建网站公司,优化营商环境应当坚持什么原则,如何使用上线了app建设网站,番禺网站建设三杰科技C17引入了std::filesystem库(文件系统库, filesystem library)#xff0c;相关类及函数的声明在头文件filesystem中#xff0c;命名空间为std::filesystem。 1.path类#xff1a;文件路径相关操作#xff0c;如指定的路径是否存在等#xff0c;其介绍参见#xff1a;http… C17引入了std::filesystem库(文件系统库, filesystem library)相关类及函数的声明在头文件filesystem中命名空间为std::filesystem。 1.path类文件路径相关操作如指定的路径是否存在等其介绍参见https://blog.csdn.net/fengbingchun/article/details/133217504 2.directory_entry类获取文件属性等,如指定文件是否是常规文件还包括文件大小、文件最后修改时间其介绍参见https://blog.csdn.net/fengbingchun/article/details/133430293 3.directory_iterator类遍历目录获取目录文件不包括子目录其介绍参见https://blog.csdn.net/fengbingchun/article/details/133437356 4.recursive_directory_iterator类遍历目录获取目录文件包括子目录其介绍参见https://blog.csdn.net/fengbingchun/article/details/133437356 5.filesystem_error类异常类继承自std::system_error继承关系如下图所示 (1).path1, path2返回存储在异常对象中的path (2).what: 返回解释性字符串 (3).code: 返回错误码。 测试代码如下所示
int test_filesystem_filesystem_error()
{// path1, path2, whtat// creates a unique filename that does not name a currently existing fileconst fs::path oldp{ std::tmpnam(nullptr) }, newp{ std::tmpnam(nullptr) };/* windows:what(): rename: 系统找不到指定的文件。: C:\Users\f06190\AppData\Local\Temp\sf2w.0, C:\Users\f06190\AppData\Local\Temp\sf2w.1path1(): C:\\Users\\f06190\\AppData\\Local\\Temp\\sf2w.0path2(): C:\\Users\\f06190\\AppData\\Local\\Temp\\sf2w.1 *//* linuxwhat(): filesystem error: cannot rename: No such file or directory [/tmp/filezJrUkO] [/tmp/filey7tqKV]path1(): /tmp/filezJrUkOpath2(): /tmp/filey7tqKV */try {fs::rename(oldp, newp); // throws since oldp does not exist} catch (fs::filesystem_error const ex) {std::cout what(): ex.what() \n path1(): ex.path1() \n path2(): ex.path2() \n;}return 0;
} 6.file_status类获取或设置有关文件类型(type)和权限(permissions)的信息 (1).type: 获取或设置文件类型信息 (2).permissions: 获取或设置文件权限信息。 测试代码如下所示
void demo_status(const fs::path p, fs::file_status s)
{std::cout p;switch (s.type()) {case fs::file_type::none:std::cout has not-evaluated-yet type;break;case fs::file_type::not_found:std::cout does not exist;break;case fs::file_type::regular:std::cout is a regular file;break;case fs::file_type::directory:std::cout is a directory;break;case fs::file_type::symlink:std::cout is a symlink;break;case fs::file_type::block:std::cout is a block device;break;case fs::file_type::character:std::cout is a character device;break;case fs::file_type::fifo:std::cout is a named IPC pipe;break;case fs::file_type::socket:std::cout is a named IPC socket;break;case fs::file_type::unknown:std::cout has unknown type;break;default:std::cout has implementation-defined type;break;}std::cout \n;
}void demo_perms(fs::perms p)
{using fs::perms;auto show [](char op, perms perm) {std::cout (perms::none (perm p) ? - : op);};show(r, perms::owner_read);show(w, perms::owner_write);show(x, perms::owner_exec);show(r, perms::group_read);show(w, perms::group_write);show(x, perms::group_exec);show(r, perms::others_read);show(w, perms::others_write);show(x, perms::others_exec);std::cout \n;
}int test_filesystem_file_status()
{
#ifdef _MSC_VERconst std::string path{ ../../../testdata/list.txt };
#elseconst std::string path{ ../../testdata/list.txt };
#endif// 1. type// windows: ../../../testdata/list.txt is a regular file// linux: ../../testdata/list.txt is a regular filedemo_status(path, fs::status(path));// 2. permissionsdemo_perms(fs::status(path).permissions()); // rwxrwxrwxreturn 0;
} 7.space_info结构体获取有关文件系统上的空闲(free)和可用空间(available space)的信息
struct space_info {std::uintmax_t capacity; // 总大小以字节为单位std::uintmax_t free; // 可用空间以字节为单位std::uintmax_t available; // 非特权进程可用的可用空间(可能等于或小于可用空间)
};
float get_file_size(std::uintmax_t size, std::string suffix)
{float s1 size / 1024. / 1024 / 1024;float s2 size / 1024. / 1024;float s3 size / 1024.;if (s1 1) {suffix GB;return s1;}if (s2 1) {suffix MB;return s2;}if (s3 1) {suffix KB;return s3;}suffix Bytes;return size;
}int test_filesystem_space_info()
{fs::space_info info fs::space(fs::current_path());std::cout current path: fs::current_path() ;// windows: current path: E:\\GitCode\\Messy_Test\\prj\\x86_x64_vc12\\CppBaseTest size: 311.00 GB size: 189.23 GB size: 189.23 GB// linux: current path: /home/spring/GitCode/Messy_Test/prj/linux_cmake_CppBaseTest size: 311.00 GB size: 189.23 GB size: 189.23 GBfor (auto x : { info.capacity, info.free, info.available }) {std::string suffix;auto value get_file_size(static_caststd::intmax_t(x), suffix);std::cout size: std::fixed std::setprecision(2) value suffix ;}std::cout std::endl;return 0;
} 8.file_type枚举类文件的类型
enum class file_type {none /* unspecified */,not_found /* unspecified */,regular /* unspecified */,directory /* unspecified */,symlink /* unspecified */,block /* unspecified */,character /* unspecified */,fifo /* unspecified */,socket /* unspecified */,unknown /* unspecified */,/* implementation-defined */
}; 9.perms枚举类文件访问权限如下图所示 10.perm_options枚举类控制函数std::filesystem::permissions()行为的可用选项如下图所示
enum class perm_options {replace /* unspecified */,add /* unspecified */,remove /* unspecified */,nofollow /* unspecified */
}; 11.非成员函数 (1).absolute:返回绝对路径 (2).canonical, weakly_canonical: 将指定路径转换为规范绝对路径(canonical absolute path)指定的路径必须存在 (3).relative, proximate: 返回相对路径 (4).copy: 拷贝文件或目录会生成新的文件或目录from指定的文件或目录必须存在to指定的文件或目录必须不存在 (5).copy_file: 拷贝文件会生成新的文件from指定的文件必须存在to指定的文件必须不存在若发生错误则返回false (6).copy_symlink拷贝符号链接 (7).create_directory, create_directories: 创建新目录使用create_directory时要求父目录必须已存在即create_directory不支持多级创建而create_directories没有这些限制 (8).create_hard_link创建硬链接 (9).create_symlink, create_directory_symlink: 创建符号链接 (10).current_path: 获取当前工作目录 (11).exists: 检查指定的文件或目录是否存在 (12).equivalent: 检查两个路径是否是相同的 (13).file_size: 获取文件大小 (14).hard_link_count: 获取指定路径硬链接数 (15).last_write_time: 获取或设置指定路径最后一次修改时间 (16).permissions: 修改文件访问权限 (17).read_symlink: 获取符号链接的target (18).remove, remove_all删除文件或空目录remove_all可递归地删除文件或目录及其所有内容并返回已删除的文件和目录的数量 (19).rename: 重命名文件或目录 (20).resize_file: 更改常规文件大小 (21).space: 获取指定的路径的可用空间 (22).status, symlink_status: 获取文件属性如指定路径是否是常规文件、是否是目录等 (23).temp_directory_path: 返回适合临时文件的目录。 std::error_code类是与平台相关的错误码。std::filesystem中的所有函数都有一个对应非抛出异常的对等接口。 测试代码如下所示
int test_filesystem_non_member_functions()
{const fs::path p1 ../funset.cpp;
#ifdef _MSC_VERconst fs::path p2{ ../../../testdata/list.txt }, p3{ ../../../testdata/list_copy.txt }, p4{ E:\\yulong.mp4 }, p5{ ../../../testdata/list_new.txt };
#elseconst fs::path p2{ ../../testdata/list.txt }, p3{ ../../testdata/list_copy.txt }, p4{ ./build/CppBaseTest }, p5{../../testdata/list_new.txt};
#endif// windows: current path is E:\\GitCode\\Messy_Test\\prj\\x86_x64_vc12\\CppBaseTest// linux: current path is /home/spring/GitCode/Messy_Test/prj/linux_cmake_CppBaseTeststd::cout current path is fs::current_path() \n;// 1. absolute// windows: absolute path for ../funset.cpp is E:\\GitCode\\Messy_Test\\prj\\x86_x64_vc12\\funset.cpp// linux: absolute path for ../funset.cpp is /home/spring/GitCode/Messy_Test/prj/linux_cmake_CppBaseTest/../funset.cppstd::cout absolute path for p1 is fs::absolute(p1) \n;// 2. canonical, weakly_canonical/* windows:canonical path: E:\\GitCode\\Messy_Test\\testdata\\list.txtweakly canonical path: E:\\GitCode\\Messy_Test\\testdata\\list.txt *//* linux:canonical path: /home/spring/GitCode/Messy_Test/testdata/list.txtweakly canonical path: /home/spring/GitCode/Messy_Test/testdata/list.txt */std::cout canonical path: fs::canonical(p2) \n;std::cout weakly canonical path: fs::weakly_canonical(p2) \n;// 3. relative, proximatestd::cout relative path: fs::relative(/a/b/c, /a/b) , proximat path: fs::proximate(/a/b/c, /a/b) \n; // relative path: c, proximat path: c// 4. copy, exists, removeif (fs::exists(p3))fs::remove(p3);fs::copy(p2, p3);// 5. copy_fileif (fs::exists(p3))fs::remove(p3);fs::copy_file(p2, p3);// 6. create_directory, create_directoriesfs::create_directory(./a);fs::create_directories(./b/c/d);// 7. equivalentif (fs::equivalent(., fs::current_path()))std::cout they are equal \n;// 8. file_sizestd::string suffix;auto value get_file_size(static_caststd::intmax_t(fs::file_size(p4)), suffix);// windows: size: 1.35 GB; linux: size: 7.61 MBstd::cout size: std::fixed std::setprecision(2) value suffix \n;// 9. last_write_time// windows: last write time: 2023-08-19 22:42:56// linux: last write time: 2023-10-03 12:32:49std::cout last write time: to_time_t(last_write_time(p4)) std::endl;// 10. permissions// windows: rwxrwxrwx r-xr-xr-x// linux: rw-rw-r-- -w-r-----demo_perms(fs::status(p3).permissions());
#ifdef _MSC_VERfs::permissions(p3, fs::perms::none);
#elsefs::permissions(p3, fs::perms::owner_write | fs::perms::group_read);
#endifdemo_perms(fs::status(p3).permissions());// 11. renameif (fs::exists(p5))fs::remove(p5);fs::rename(p3, p5);// 12. resize_file// linux: size: 187.00 Bytes size: 64.00 KBvalue get_file_size(static_caststd::intmax_t(fs::file_size(p5)), suffix);std::cout size: std::fixed std::setprecision(2) value suffix \n;
#ifdef __linux__fs::resize_file(p5, 64 * 1024); // resize to 64 KB, windows crashvalue get_file_size(static_caststd::intmax_t(fs::file_size(p5)), suffix);std::cout size: std::fixed std::setprecision(2) value suffix \n;
#endif// 13. temp_directory_path// windows: temp directory is: C:\\Users\\f06190\\AppData\\Local\\Temp\\// linux: temp directory is: /tmpstd::cout temp directory is: fs::temp_directory_path() \n;// std::error_codestd::error_code ec;fs::copy_file(xxx, yyy, ec); // does not throw// windows: error code: 2,系统找不到指定的文件。// linux: error code: 2,No such file or directorystd::cout error code: ec.value() , ec.message() \n;try {fs::copy_file(xxx, yyy);} catch (fs::filesystem_error const ex) {std::cout what(): ex.what() \n path1(): ex.path1() \n path2(): ex.path2() \n code().value(): ex.code().value() \n code().message(): ex.code().message() \n code().category(): ex.code().category().name() \n;}return 0;
} 执行结果如下图所示 12.文件类型 (1).is_block_file: 检查给定的文件或路径是否是块设备 (2).is_character_file: 检查给定的文件或路径是否是字符设备 (3).is_directory: 检查给定的文件或路径是否是目录 (4).is_empty: 检查给定的文件或路径是否是空文件或空目录 (5).is_fifo: 检查给定的文件或路径是否是命名管道 (6).is_other: 检查给定的文件或路径是否是其它文件 (7).is_regular_file: 检查给定的文件或路径是否是常规文件 (8).is_socket: 检查给定的文件或路径是否是套接字 (9).is_symlink: 检查给定的文件或路径是否是符号链接 (10).status_known: 检查给定的文件是否已知。 测试代码如下所示
void demo_status2(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;//if (fs::is_empty(p))// std::cout is empty\n;if (fs::is_other(s)) // equivalent to exists(s) !is_regular_file(s) !is_directory(s) !is_symlink(s)std::cout is other file\n;//if (fs::status_known(s)) // equivalent to s.type() ! file_type::none// std::cout is status known\n;
}int test_filesystem_file_types()
{demo_status2(/dev/null, fs::status(/dev/null));demo_status2(/dev/sda, fs::status(/dev/sda));demo_status2(fs::current_path(), fs::status(fs::current_path()));demo_status2(/xxx/yyy, fs::status(/xxx/yyy));demo_status2(/usr/bin/g, fs::status(usr/bin/g));demo_status2(../../../testdata/list.txt, fs::status(../../../testdata/list.txt));demo_status2(../../testdata/list.txt, fs::status(../../testdata/list.txt));demo_status2(/mnt, fs::status(/mnt));return 0;
} GitHubhttps://github.com/fengbingchun/Messy_Test
