UNIX for Dummies Questions & Answers

How is the level of access on a particular folder determined? I have heard (its just hearsay so am not particularly sure of it) that the access a particular user/group has to a low level directory is also affected by the level of access granted to the user/group on its parent directories. e.g.

If user has read and write access on

Code:

/usr/local/temp/a

but no access on

Code:

/usr/local/temp

will he/she/it still be able to read and write files on /usr/local/temp/a?

What logic (if any) is used here to determine the level of access? And is it different for individual users and application accounts (which intuition tells me are one and the same thing for the OS)?

Just to scan subdirectories requires execute + read (rwxr-xr-x) on the parent directory. And all directories in the path to the file. This example allows anyone on the machine to

Code:

ls /usr/local/temp/a/*

If you already know the filename then this works for the parent and all the other directories in the path : (rwx--x--x)

Code:

ls /usr/local/temp/a/myfilename

read access is required to "scan" the directory.