On 2020-10-08 10:28, Tomás Fernandes wrote:
Hello,
I've recently come across chmod's man page as someone who is not very
experienced (1st year CS undergrad), and found that the definition of
the
letter X in the man page a bit unclear, more specifically this part (in
bold):
On the topic of chmod documentation, it could use a clarification in the
following matter.
chmod supports a = operator for copying permissions. For instance
u=g means "make the u permissions be like g".
chmod also supports multiple operations, like
u=g,g=o
The behavior of GNU Coreutils chmod is that the = operator samples the
most *new* value of the permissions (everything to the left has already
taken place). This is true even without the comma separation, when =
is combined in one clause with other operators, as in:
o+x=o
Here, the o+x will apply the x permission to o. Then this effect is
settled
and the =o assignment therefore has no effect; it's the same as:
o+x,o=o
Or something like that; I've not looked at this stuff in a while,
but it was one of the issues I ran into when making a chmod
implementation.
It would be good if the documentation spelled it out that = references
the new permissions which result from everything to the left of =
having been processed.
