Function openat [src]

Open and possibly create a file. Keeps trying if it gets interrupted. file_path is relative to the open directory handle dir_fd. On Windows, file_path should be encoded as WTF-8. On WASI, file_path should be encoded as valid UTF-8. On other platforms, file_path is an opaque sequence of bytes with no particular encoding. See also openatZ.

Prototype

pub fn openat(dir_fd: fd_t, file_path: []const u8, flags: O, mode: mode_t) OpenError!fd_t

Parameters

dir_fd: fd_tfile_path: []const u8flags: Omode: mode_t

Possible Errors

AccessDenied

In WASI, this error may occur when the file descriptor does not hold the required rights to open a new resource relative to it.

BadPathName

Path contains characters that are disallowed by the underlying filesystem.

DeviceBusy

FileBusy

One of these three things:

pathname refers to an executable image which is currently being executed and write access was requested.
pathname refers to a file that is currently in use as a swap file, and the O_TRUNC flag was specified.
pathname refers to a file that is currently being read by the kernel (e.g., for module/firmware loading), and write access was requested.

FileLocksNotSupported

The underlying filesystem does not support file locks

FileNotFound

Either:

One of the path components does not exist.
Cwd was used, but cwd has been deleted.
The path associated with the open directory handle has been deleted.
On macOS, multiple processes or threads raced to create the same file with O.EXCL set to false.

FileTooBig

The file is too large to be opened. This error is unreachable for 64-bit targets, as well as when opening directories.

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/

IsDir

The path refers to directory but the DIRECTORY flag was not provided.

NameTooLong

The path exceeded max_path_bytes bytes.

NetworkNotFound

On Windows, \\server or \\server\share was not found.

NoDevice

NoSpaceLeft

A new path cannot be created because the device has no room for the new file. This error is only reachable when the CREAT flag is provided.

NotDir

A component used as a directory in the path was not, in fact, a directory, or DIRECTORY was specified and the path was not a directory.

PathAlreadyExists

The path already exists and the CREAT and EXCL flags were provided.

PermissionDenied

ProcessFdQuotaExceeded

SymLinkLoop

SystemFdQuotaExceeded

SystemResources

Insufficient kernel memory was available, or the named file is a FIFO and per-user hard limit on memory allocation for pipes has been reached.

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.

WouldBlock

Source

  pub fn openat(dir_fd: fd_t, file_path: []const u8, flags: O, mode: mode_t) OpenError!fd_t {
    if (native_os == .windows) {
        @compileError("Windows does not support POSIX; use Windows-specific API or cross-platform std.fs API");
    } else if (native_os == .wasi and !builtin.link_libc) {
        // `mode` is ignored on WASI, which does not support unix-style file permissions
        const opts = try openOptionsFromFlagsWasi(flags);
        const fd = try openatWasi(
            dir_fd,
            file_path,
            opts.lookup_flags,
            opts.oflags,
            opts.fs_flags,
            opts.fs_rights_base,
            opts.fs_rights_inheriting,
        );
        errdefer close(fd);

        if (flags.write) {
            const info = try std.os.fstat_wasi(fd);
            if (info.filetype == .DIRECTORY)
                return error.IsDir;
        }

        return fd;
    }
    const file_path_c = try toPosixPath(file_path);
    return openatZ(dir_fd, &file_path_c, flags, mode);
}  