Function faccessat [src]

Check user's permissions for a file, based on an open directory handle. On Windows, asserts path is valid WTF-8. On WASI, invalid UTF-8 passed to path causes error.InvalidUtf8. On other platforms, path is an opaque sequence of bytes with no particular encoding. On Windows, mode is ignored. This is a POSIX API that is only partially supported by Windows. See fs for the cross-platform file system API.

Prototype

pub fn faccessat(dirfd: fd_t, path: []const u8, mode: u32, flags: u32) AccessError!void

Parameters

dirfd: fd_tpath: []const u8mode: u32flags: u32

Possible Errors

AccessDenied

BadPathName

FileBusy

FileNotFound

InputOutput

InvalidUtf8

WASI-only; file paths must be valid UTF-8.

InvalidWtf8

Windows-only; file paths provided by the user must be valid WTF-8. https://simonsapin.github.io/wtf-8/

NameTooLong

PermissionDenied

ReadOnlyFileSystem

SymLinkLoop

SystemResources

Unexpected UnexpectedError

The Operating System returned an undocumented error code.

This error is in theory not possible, but it would be better to handle this error than to invoke undefined behavior.

When this error code is observed, it usually means the Zig Standard Library needs a small patch to add the error code to the error set for the respective function.

Source

  pub fn faccessat(dirfd: fd_t, path: []const u8, mode: u32, flags: u32) AccessError!void {
    if (native_os == .windows) {
        const path_w = try windows.sliceToPrefixedFileW(dirfd, path);
        return faccessatW(dirfd, path_w.span().ptr);
    } else if (native_os == .wasi and !builtin.link_libc) {
        const resolved: RelativePathWasi = .{ .dir_fd = dirfd, .relative_path = path };

        const st = try std.os.fstatat_wasi(dirfd, path, .{
            .SYMLINK_FOLLOW = (flags & AT.SYMLINK_NOFOLLOW) == 0,
        });

        if (mode != F_OK) {
            var directory: wasi.fdstat_t = undefined;
            if (wasi.fd_fdstat_get(resolved.dir_fd, &directory) != .SUCCESS) {
                return error.AccessDenied;
            }

            var rights: wasi.rights_t = .{};
            if (mode & R_OK != 0) {
                if (st.filetype == .DIRECTORY) {
                    rights.FD_READDIR = true;
                } else {
                    rights.FD_READ = true;
                }
            }
            if (mode & W_OK != 0) {
                rights.FD_WRITE = true;
            }
            // No validation for X_OK

            // https://github.com/ziglang/zig/issues/18882
            const rights_int: u64 = @bitCast(rights);
            const inheriting_int: u64 = @bitCast(directory.fs_rights_inheriting);
            if ((rights_int & inheriting_int) != rights_int) {
                return error.AccessDenied;
            }
        }
        return;
    }
    const path_c = try toPosixPath(path);
    return faccessatZ(dirfd, &path_c, mode, flags);
}  