shell指定参数名传参

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 ]