The
setmode() function accepts a string representation of a file mode change, compiles it to binary form, and returns an abstract representation that may be passed to
getmode(). The string may be an numeric (octal) or symbolic string of the form accepted by
chmod(1), and may represent either an exact mode to set or a change to make to the existing mode.
The
getmode() function adjusts the file permission bits given by
mode according to the compiled change representation
set, and returns the adjusted mode. While only the permission bits are altered, other parts of the file mode, particularly the type, may be examined.
Because some of the possible symbolic values are defined relative to the file creation mask,
setmode() may call
umask(2), temporarily changing the mask. If this occurs, the file creation mask will be restored before
setmode() returns. If the calling program changes the value of its file creation mask after calling
setmode(),
setmode() must be called again to recompile the mode string if
getmode() is to modify future file modes correctly.
If the mode passed to
setmode() is invalid,
setmode() returns
NULL.