方法一：使用字符串过滤出非0到9之间的字符。
[root@managevm1 ~]# a=123
[root@managevm1 ~]# echo $a | grep "[^0-9]" && echo "a isn't an integer" \
|| echo "a is an integer"
a is an integer
[root@managevm1 ~]# a=123.4
[root@managevm1 ~]# echo $a | grep "[^0-9]" && echo "a isn't an integer" \
|| echo "a is an integer"
a isn't an integer
也可以写为
[root@managevm1 ~]# echo $a | grep -v "[0-9]*" && echo "a isn't an integer"\
|| echo "a is an integer"
方法二：使用条件判断，$a中0到9出现一次以上，且不包含其他字符。
[root@managevm1 ~]# a=123
[root@managevm1 ~]# if [[ $a =~ ^[0-9]\{1,\}$ ]]; then echo "a is an integer;"\
else echo "a is not an integer"; fi
a is an integer
[root@managevm1 ~]# a=123.4
[root@managevm1 ~]# if [[ $a =~ ^[0-9]\{1,\}$ ]]; then echo "a is an integer;"\
else echo "a is not an integer"; fi
a is not an integer
这个命令也可以简单写成
[root@managevm1 ~]# [[ $a =~ ^[0-9]*$ ]] && echo "a is an integer" || \
echo "a is not an integer"
方法三：awk过滤
[root@managevm1 ~]# echo $a|awk '/^[0-9]*$/{print "a is an integer"}'
a is an integer
或写成
[root@managevm1 ~]# echo $a|awk '{if ($1~/^[0-9]*$/) print "a is an integer"}'
a is an integer方法四:使用命令bc来计算，因为shell不支持浮点预算，非整数a的值除1后会得到整数部分与原值不符合
注意这里使用 == 是做字符串的比较非数值比较。数值比较用 -eq ， 不支持浮点。
[root@managevm1 ~]# a=123
[root@managevm1 ~]# [ $(echo $a/1|bc) == "$a" ] && echo "It's an integer" \
|| echo "It's not an integer"
It's an integer
[root@managevm1 ~]# a=123.4
[root@managevm1 ~]# [ $(echo $a/1|bc) == "$a" ] && echo "It's an integer" \
|| echo "It's not an integer"
It's not an integer方法五：利用test下不支持浮点数比较的特性，通过命令的返回状态来判断。
[root@managevm1 ~]# a=123
[root@managevm1 ~]# [ $a -ge 0 ] 2>/dev/null && echo "A is an integer"|| \
echo "a is NOT an integer"
A is an integer
[root@managevm1 ~]# a=123.4
[root@managevm1 ~]# [ $a -ge 0 ] 2>/dev/null && echo "A is an integer"|| \
echo "a is NOT an integer"
a is NOT an integer来源：51CTO
作者：深蓝L
链接：https://blog.51cto.com/14316149/2475158