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PROC_COMPARE(3)            Library Functions Manual            PROC_COMPARE(3)

NAME
     proc_compare - compare two processes' interactivity

LIBRARY
     System Utilities Library (libutil, -lutil)

SYNOPSIS
     #include <sys/sysctl.h>

     int
     proc_compare(const struct kinfo_proc2 *p1, const struct kinfo_lwp *l1,
         const struct kinfo_proc2 *p2, const struct kinfo_lwp *l2);

DESCRIPTION
     The proc_compare() function compares two processes that are on the same
     terminal for their interactivity.  This means that the process returned
     is the one that has a better chance being the active foreground process
     on that tty.  This algorithm is used in the kernel for SIGINFO reporting
     and in userland by w(1).

     The algorithm used is as follows:
           ⊕   If one of them is runnable, it is preferred.
           ⊕   If both are runnable, the one with the largest CPU percent is
               preferred.
           ⊕   In a CPU percent tie, the one started more recently wins.
           ⊕   If none are runnable, and one of them is a zombie, the non-
               zombie is preferred
           ⊕   If both are zombies, the one started more recently wins.
           ⊕   If neither is a zombie, the one with the smaller sleep time
               wins.
           ⊕   In a tie, and one is sleeping in non-interruptible sleep,
               prefer that one.
           ⊕   If both are in the same state, the one started more recently is
               preferred.
     In all cases where the most recently started wins, if there was no
     winner, the one with the largest PID wins.

RETURN VALUES
     The proc_compare() function returns 0 if p1 is to be preferred and 1 if
     p2 is to be preferred.

SEE ALSO
     w(1)

HISTORY
     The proc_compare() was extracted from src/sys/kern/tty.c and
     src/usr.bin/w/proc_compare.c and merged in NetBSD 6.0.

NetBSD 10.99                   October 20, 2011                   NetBSD 10.99