如何让getopts必选选项强制带有效参数，避免参数误识别？

The issue you're hitting is a common gotcha with getopts: when an option expects an argument but you don't provide one, it will greedily take the next command-line token (even if it's another option starting with -) as its argument. To fix this, we need to add immediate validation for your mandatory -i option's argument, plus keep the post-option-check for the mandatory flag itself.

Here's the revised test.sh script with strict validation:

#!/bin/bash

# Initialize mandatory variable to empty
thefile=""

while getopts "i:n:d:r:p:s:l:h" opt; do
    case $opt in
        i) 
            # Check if the argument is another option (starts with -)
            if [[ "$OPTARG" == -* ]]; then
                echo "Error: Option -i requires a valid file path, not another option '$OPTARG'" >&2
                exit 1
            fi
            # Also ensure the argument isn't empty (though getopts usually prevents this)
            if [[ -z "$OPTARG" ]]; then
                echo "Error: Option -i cannot have an empty argument" >&2
                exit 1
            fi
            thefile=$OPTARG
            ;;
        n) size=$OPTARG;;
        d) dmax=$OPTARG;;
        r) rmsd=$OPTARG;;
        p) penalty=$OPTARG;;
        s) sampling=$OPTARG;;
        l) log=$OPTARG;;
        h) 
            printf "Usage: `basename $0` options -i [input_file.txt]\n \
                -i 输入文件（必选）\n \
                -n 尺寸\n \
                -d 距离\n \
                -r rflag\n \
                -p pflag \n \
                -l 0/1用于生成日志文件（可选，默认=1）\n \
                -h 查看帮助 \n"
            exit 0
            ;;
        \? ) echo "Unknown option: -$OPTARG" >&2; exit 1;;
        : ) echo "Missing option argument for -$OPTARG" >&2; exit 1;;
        * ) echo "Unimplemented option: -$OPTARG" >&2; exit 1;;
    esac
done

# Final check to ensure -i was provided with a valid value
if [[ -z "$thefile" ]]; then
    echo "Error: Mandatory option -i must be specified with a file path" >&2
    exit 1
fi

# Rest of your script logic here
echo "Input file set to: $thefile"

Key Improvements: #

• Immediate argument validation for -i: When processing the -i option, we check if the argument starts with - (indicating it's another option, not a file path). This catches cases like ./test.sh -i -n 4 immediately.
• Explicit mandatory check: After processing all options, we verify that thefile isn't empty, ensuring -i was actually provided (not just skipped entirely).
• Clearer help text: Added a note that -i is mandatory to make usage expectations obvious.

Test Cases: #

1. Invalid usage (missing -i argument):

   ./test.sh -i -n 4
   

   Output:

   Error: Option -i requires a valid file path, not another option '-n'
   

2. Missing mandatory -i:

   ./test.sh -n 4
   

   Output:

   Error: Mandatory option -i must be specified with a file path
   

3. Valid usage:

   ./test.sh -i input.txt -n 4
   

   Output:

   Input file set to: input.txt
   

This approach ensures your mandatory options are used correctly, with valid arguments that don't get confused with other command-line flags.

内容的提问来源于stack exchange，提问作者blehblehblecksheep