（4）编写一个shell脚本，以英文月份名为参数，显示当年该月的日历。

Sure, I can help you with that! Here's a simple shell script (bash) that takes an English month name as an argument and displays the calendar for that month:

#!/bin/bash

# Function to get the number of days in a month based on its name
get_days_in_month() {
  case "$1" in
    "January"|"March"|"May"|"July"|"August"|"October"|"December")
      echo 31
    ;;
    "April"|"June"|"September"|"November")
      echo 30
    ;;
    "February")
      if [ $(date +%Y) -eq $(date -d "$1 01 +1 year" +%Y) ]; then
        echo 29 # Leap year
      else
        echo 28
      fi
    ;;
    *)
      echo "Invalid month name"
      exit 1
    ;;
  esac
}

# Check if the argument is a valid month name
if [[ ! "$#" -eq 1 || ! "${MONTHS[@]}" =~ ^$1$ ]]; then
  echo "Usage: $0 <month_name>"
  exit 1
fi

month=$(echo $1 | tr '[:upper:]' '[:lower:]')
days=$(get_days_in_month "$month")

# Display the calendar using cal command (assuming it's installed)
cal -j "$month" "$(expr 1 - $month)"

To use this script, save it as a file like `calendar.sh`, give it execute permissions (`chmod +x calendar.sh`), and run it with the desired month name as an argument, e.g., `./calendar.sh february`.

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