$ ); echo $? echoed 0,all other shells echo 2.

[unix-history] / usr / src / bin / sh / trap.h

/*-
* Copyright (c) 1991, 1993
*      The Regents of the University of California.  All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Kenneth Almquist.
*
* %sccs.include.redist.c%
*
*      @(#)trap.h      8.2 (Berkeley) %G%
*/

extern int pendingsigs;

int trapcmd __P((int, char **));
void clear_traps __P((void)); 
long setsignal __P((int)); 
sig_t getsigaction __P((int));
void ignoresig __P((int));
void onsig __P((int));
void dotrap __P((void));
void setinteractive __P((int));
void exitshell __P((int));