如果您有比较丰富的 shell 脚本编程经验，可能能够读懂这个脚本。但是，脚本编程的初学者很难理解这个函数的作用。如果花上几分钟在这个脚本中添加注释，情况就大不一样了。清单 7 给出包含注释的同一个函数。

　　清单 7. 包含注释的脚本示例

#########################################
# function confirm_and_exit
#########################################
confirm_and_exit() {
　# if the debug level is set to 3 or higher, send every evaluated line to stdout
　[[ ${_DEBUG_LEVEL} -ge 3 ]] && set –x
　# Continue to prompt the user until they provide a valid answer
　while [[ -z ${_EXIT_ANS} ]]
　do
　　# prompt user if they want to exit the script
　　# cup_echo function calls tput cup <x> <y>
　　# syntax:
　　# cup_echo <string to display> <row on stdout to display>
　　　　<column on stdout to display>
　　cup_echo "Are you sure you want to exit? [Y/N]　
　　　　c" ${_PROMPT_ERR_ROW} ${_PROMPT_ERR_COL}
　　# change cursor to normal via tput
　　${_TPUT_CMD} cnorm
　　# read value entered by user
　　# if _NO_EOL_FLAG is supplIEd, use value of _READ_FLAG or “-n
　　# if _NO_EOL_FLAG is supplied, use value as characters aloud on read
　　# assign value entered by user to variable _EXIT_ANS
　　read ${_NO_EOL_FLAG:+${_READ_FLAG:-'-n'}} ${_NO_EOL_FLAG} _EXIT_ANS
　　# change cursor to invisible via tput
　　${_TPUT_CMD} civis
　done
　# if user entered “n, return to previous block of code with return code 0
　# if user entered “y, exit the script
　# if user entered anything else, execute function invalid_selection
　case ${_EXIT_ANS} in
　　[Nn])　unset _EXIT_ANS; return 0;;
　　[Yy])　exit_msg 0 1 "Exiting Script";;
　　　 *)　invalid_selection ${_EXIT_ANS}; unset _EXIT_ANS;;
　esac
　# exit function with return code 0
　return 0
}

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