Access Modes Details
r - Read mode
Allows the program to have read access to the file or directory
listing. Read access is required for shell scripts and other
w - Write mode
Allows the program to have write access to the file. Files and
directories must have this permission if they are to be unlinked
(removed.) Write mode is not required on a directory to rename or
create files within the directory.
This mode conflicts with append mode.
a - Append mode
Allows the program to have a limited appending only write access to
the file. Append mode will prevent an application from opening the
file for write unless it passes the O_APPEND parameter flag on
The mode conflicts with Write mode.