问在bash中调用在base64中解码的函数

EN

#!/bin/bash

#if there are no args supplied exit with 1
if [ "$#" -eq 0 ]; then
        echo "Unfortunately you have not passed any parameter"
        exit 1
fi

#loop over each argument
for arg in "$@"
do
    if [ -f arg ]; then
                echo "$arg is a file."

                #iterates over the files stated in arguments and reads them    $
                cat $arg | while read line;
                do
                    #should access only first line of the file
                        if [ head -n 1 "$arg" ]; then
                                process line
                                echo "Script has ran successfully!"
                                exit 0
                        #should access only last line of the file
                        elif [ tail -n 1 "$arg" ]; then
                                process line
                                echo "Script has ran successfully!"
                                exit 0
                        #if it accesses any other line of the file
                        else
                                echo "We only process the first and the last line of the file."
                        fi
                done
        else
                exit 2
        fi
done

#function to process the passed string and decode it in base64
process()   {
        string_to_decode = "$1"
        echo "$string_to_decode = " | base64 --decode
}

first_line = $(head -n 1 "$arg")
                    last_line = $(tail -n 1 "$arg")
                    if [ first_line == line ]; then
                            process line
                            echo "Script has ran successfully!"
                            exit 0
                    #should access only last line of the file
                    elif [ last_line == line ]; then
                            process line
                            echo "Script has ran successfully!"
                            exit 0

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MTBkb3duaW5nc3RyZWV0Lmdvdi51awo=
MXZhbGUuZ292LnVrCg==