trap.err

UNIX+shell范例精解（第4版）代码

#!/bin/ksh
# This trap checks for any command that exits with a non-zero 	
# status and then prints the message.
trap 'print "You gave me a non-integer. Try again. "' ERR
typeset -i number     # Assignment to number must be integer
while true
do
    print -n "Enter an integer. " 
    read -r number 2> /dev/null
    if (( $? == 0 ))     # Was an integer read in? 
    then                 # Was the exit status zero?
        break 
    fi
done
trap - ERR           # Unset pseudo trap for ERR
n=$number
if grep ZOMBIE /etc/passwd > /dev/null 2>&1
then
 	:  
else
    print "\$n is $n. So long"
fi