$unix:umask¶

The file mode creation mask. Its value is a string in Elvish octal representation; e.g. 0o027. This makes it possible to use it in any context that expects a $number.

When assigning a new value a string is implicitly treated as an octal number. If that fails the usual rules for interpreting numbers are used. The following are equivalent: unix:umask = 027 and unix:umask = 0o27. You can also assign to it a float64 data type that has no fractional component. The assigned value must be within the range [0 ... 0o777], otherwise the assignment will throw an exception.

You can do a temporary assignment to affect a single command; e.g. umask=077 touch a_file. After the command completes the old umask will be restored. Warning: Since the umask applies to the entire process, not individual threads, changing it temporarily in this manner is dangerous if you are doing anything in parallel. Such as via the peach command.