arguments

command itself: $0
Example:
DIR=`dirname $0`

input arguments: $@
Example:
for URL in "$@"
do
echo $URL >> $URLFILE
done

use the ${LIST:2} to skip the 1st param
Example:
#!/bin/bash
EVAL=$1
CMD="$EVAL ${@:2}"
echo "$CMD"

judge if argument exists: -z
Example:
if [ -z $2 ]; then
URLFILE=$2
fi

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