.\" Copyright (c) 1991 The Regents of the University of California.
.\" This code is derived from software contributed to Berkeley by
.\" the American National Standards Committee X3, on Information
.\" %sccs.include.redist.man%
.\" @(#)iscntrl.3 5.4 (Berkeley) %G%
.Nd control character test
function tests for any control character.
In the ASCII character set, this includes the following characters:
.Bl -column \&000_``0''__ \&000_``0''__ \&000_``0''__ \&000_``0''__ \&000_``0''__
.It \&000\ nul \t001\ soh \t002\ stx \t003\ etx \t004\ eot
.It \&005\ enq \t006\ ack \t007\ bel \t010\ bs \t011\ ht
.It \&012\ nl \t013\ vt \t014\ np \t015\ cr \t016\ so
.It \&017\ si \t020\ dle \t021\ dc1 \t022\ dc2 \t023\ dc3
.It \&024\ dc4 \t025\ nak \t026\ syn \t027\ etb \t030\ can
.It \&031\ em \t032\ sub \t033\ esc \t034\ fs \t035\ gs
.It \&036\ rs \t037\ us \t177\ del
function returns zero if the character tests false and
returns non-zero if the character tests true.