e less than some magic threshold value, commonly 100. This can lead to unexpected results. • The SVR4.2 shell does not allow users to trap SIGSEGV, SIGALRM, or SIGCHLD. • The SVR4.2 shell does not allow the IFS, MAILCHECK, PATH, PS1, or PS2 variables to be unset. • The SVR4.2 shell treats as the undo