Bash脚本年份输入校验问题求助：需实现2018-2099范围验证

Hey there! Let's get that year validation script working properly. Your current code has two main issues: the regex doesn't correctly enforce the 2018-2099 range, and it exits immediately instead of prompting the user to try again. Here's a revised version with explanations:

Working Script #

#!/bin/bash

# Loop until valid input is received
while true; do
    read -r -p "Type year [value from 2018-2099]: " year
    
    # First, check if input is a 4-digit number in the correct range
    if [[ "$year" =~ ^20(1[89]|[2-9][0-9])$ ]]; then
        # Optional numeric check as an extra safeguard
        if (( year >= 2018 && year <= 2099 )); then
            mkdir -p "/home/$year/"
            echo "Successfully created directory /home/$year/"
            exit 0
        fi
    fi
    
    # If we reach here, input was invalid
    echo "Error: '$year' is not a valid year. Please enter a value between 2018 and 2099." >&2
done

Key Changes Explained #

• Loop for re-entry: Used while true to keep asking for input until a valid year is provided, instead of exiting on the first mistake.
• Corrected regex: ^20(1[89]|[2-9][0-9])$ ensures:
  • The input starts with 20 (locking us into the 2000s)
  • Followed by either 18/19 (covers 2018-2019) or 20-99 (covers 2020-2099)
• Numeric range check: Added an extra numeric validation step to catch any edge cases the regex might miss (though the regex is solid, this adds robustness).
• Clear error messaging: Updated the error prompt to be more specific, so the user knows exactly what's wrong.
• Consistent range: Aligned the prompt text with your stated requirement of 2018-2099 (your original prompt mentioned 2019, which I fixed to match your goal).

Why Your Original Script Failed #

Your regex ^(20[1-9]|[1-9])+$ was matching values like 201, 205, or even single digits (e.g., 5)—it didn't enforce a 4-digit number, let alone the 2018-2099 range. Plus, there was no loop to allow re-entry, so the script just exited immediately on the first invalid input.

内容的提问来源于stack exchange，提问作者Marcin A