Shell中判断字符串是否为数字的7种方法

方法一

A=123

echo "${A}" |[ -n "sed -n '/^[0-9][0-9]*$/p'" ] && echo ${A} is a numbers

方法二

A=123

echo "${A}" |grep '^[[:digit:]]*$' >/dev/null

if [ $? -eq 0 ];then

    echo "${A} is a number."

else

    echo '${A} Not a number.'

fi

方法三

A=123

if [ "${A}" -gt 0 ] 2>/dev/null ;then

    echo "$1 is a number."

else

    echo '$1 Not a number.'

fi

方法四

case "$1" in

    [1-9][0-9]*)

    echo "$1 is number."

    ;;

    *)

    ;;

esac

方法五

A=123

echo ${A}| awk '{print($0~/^[-]?([0-9])+[.]?([0-9])+$/)?"number":"string"}'

方法六

A=123

if [ -n "$(echo ${A}| sed -n "/^[0-9]+$/p")" ];then

    echo "${A} is a number."

else

    echo "${A} not a number."

fi

方法七

A=123

expr ${A} "+" 1 &> /dev/null

if [ $? -eq 0 ];then

    echo "${A} is a number"

else

    echo "${A} not a number"

fi