APUE - jwyx/ForFun GitHub Wiki

/etc/passwd

Seven colon-separated fields:
    the login name, encrypted password, numeric user ID (205), numeric group ID (105),
    a comment field, home directory (/home/sar), and shell program (/bin/ksh)

Signal

Signals are software interrupts. Signals provide a way of handling asynchronous events.
POSIX.1 standardized the reliable signals routines and that is what we describe here.

Concepts
    Every signal has a name and these names all begin with the three characters SIG.