System calls are functions that a programmer can call to perform the services of the operating system. There are several online books that describe them at some length, for example Programming in C. Unix manual pages are probably the first stop. They are often referred to as "man pages," because they are accessed with the man command. The manual pages are divided into eight sections. They are organized as follows:read more
Traditionally, Unix/Linux/POSIX filenames can be almost any sequence of bytes, and their meaning is unassigned. The only real rules are that "/" is always the directory separator, and that filenames can't contain byte 0 (because this is the terminator). Although this is flexible, this creates many unnecessary problems. In particular, this lack of limitations makes it unnecessarily difficult to write correct programs (enabling many security flaws), makes it impossible to consistently and accurately display filenames, causes portability problems, and confuses users. more ....
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