参考：https://www.computerhope.com/unix/bash/getopts.htm
如果使用shell指定参数名称传参，是使用到了“getopts”命令，下面举个例子，定义入参（-n NAME and -t TIMES.）并获取参数，里面已包含注释：
#!/bin/bash
# 1. 定义参数变量名
NAME="" # Name of person to greet.
TIMES=1 # Number of greetings to give.
# 2. 用法提示
usage() { # Function: Print a help message.
echo "Usage: $0 [ -n NAME ] [ -t TIMES ]" 1>&2
}
exit_abnormal() { # Function: Exit with error.
usage
exit 1
}
# 3. while循环设置进定义的变量名，并校验参数的合法性
while getopts ":n:t:" options; do # Loop: Get the next option;
# use silent error checking;
# options n and t take arguments.
case "${options}" in #
n) # If the option is n,
NAME=${OPTARG} # set $NAME to specified value.
;;
t) # If the option is t,
TIMES=${OPTARG} # Set $TIMES to specified value.
re_isanum='^[0-9]+$' # Regex: match whole numbers only
if ! [[ $TIMES =~ $re_isanum ]] ; then # if $TIMES not whole:
echo "Error: TIMES must be a positive, whole number."
exit_abnormal
exit 1
elif [ $TIMES -eq "0" ]; then # If it's zero:
echo "Error: TIMES must be greater than zero."
exit_abnormal # Exit abnormally.
fi
;;
:) # If expected argument omitted:
echo "Error: -${OPTARG} requires an argument."
exit_abnormal # Exit abnormally.
;;
*) # If unknown (any other) option:
exit_abnormal # Exit abnormally.
;;
esac
done
# 4. 使用定义的变量名
if [ "$NAME" = "" ]; then # If $NAME is an empty string,
STRING="Hi!" # our greeting is just "Hi!"
else # Otherwise,
STRING="Hi, $NAME!" # it is "Hi, (name)!"
fi
COUNT=1 # A counter.
while [ $COUNT -le $TIMES ]; do # While counter is less than
# or equal to $TIMES,
echo $STRING # print a greeting,
let COUNT+=1 # then increment the counter.
done
exit 0
运行结果：
./greeting
Hi!
-----
./greeting -n Dave
Hi, Dave!
-----
./greeting -t 3
Hi!
Hi!
Hi!
-----
./greeting -t 4 -n Betty
Hi, Betty!
Hi, Betty!
Hi, Betty!
Hi, Betty!
------
./greeting -n
Error: -n requires an argument.
Usage: ./greeting [ -n NAME ] [ -t TIMES ]
------
./greeting -t
Error: -t requires an argument.
Usage: ./greeting [ -n NAME ] [ -t TIMES ]
------
./greeting -t 0
Error: TIMES must be greater than zero.
Usage: ./greeting [ -n NAME ] [ -t TIMES ]
