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Module sys/umask

sys/umask
Stability: unstable — and the open question is Windows, not the shape. Windows has no process file-creation mask, so the generated runtime keeps the value in a process-global and returns the previous one: the call SUCCEEDS and changes nothing about how files are created. A caller cannot distinguish that from a working umask, which is exactly the kind of silent divergence a frozen API should not promise. Freezing needs a decision on which way to resolve it — have the Windows `openat` path honour the stored mask, or make this POSIX-only and fail loudly elsewhere. — stable modules only change additively; this one may still change.

Process file-creation mask (umask) — the raw syscall boundary.

One thin wrapper over POSIX umask(2). There is no public std module over it yet; tests/sys/umask.test.yo is its only caller in this tree.

Stability

unstable — and the open question is Windows, not the shape. Windows has no process file-creation mask, so the generated runtime keeps the value in a process-global and returns the previous one: the call SUCCEEDS and changes nothing about how files are created. A caller cannot distinguish that from a working umask, which is exactly the kind of silent divergence a frozen API should not promise. Freezing needs a decision on which way to resolve it — have the Windows openat path honour the stored mask, or make this POSIX-only and fail loudly elsewhere.

Functions

umask function
fn(mask : i32) -> i32

Set the process file-creation mask and return the PREVIOUS one — POSIX umask(2). Bits set in mask are the permission bits cleared from the mode of newly created files, so 0o022 is the usual "group and other cannot write".

There is no failure path: umask(2) cannot fail, so the return is always the old mask and never a negative errno. Reading the current mask means setting it and setting it back.

On Windows the value is only remembered (see the module note) and nothing consults it.

Parameters

NameTypeNotes
maski32

Returns: i32