+,- *,/,% **:幂运算,最先计算。 ++,-- !,&&,|| <,>,<= ==,!=,= <<,>>:向左,右移位。 ~,|,&,^:按位取反,按位异或,按位与,按位或 =,+=,-=,*=,/=,%=
①(()) [root@centos6-kvm3 ~]# i=$a+1 [root@centos6-kvm3 ~]# echo $i 1+1 [root@centos6-kvm3 ~]# echo $((a+3)) 4 [root@centos6-kvm3 ~]# echo $((2**3)) 8 [root@centos6-kvm3 ~]# echo $((1+2**3-5%3)) 7 [root@centos6-kvm3 ~]# ((i++)) [root@centos6-kvm3 ~]# echo $i 3 ②let [root@centos6-kvm3 ~]# a=1 [root@centos6-kvm3 ~]# i=$a+1 [root@centos6-kvm3 ~]# let i=$a+1 [root@centos6-kvm3 ~]# echo $i 2 ③expr [root@centos6-kvm3 ~]# expr 2 + 3 5 [root@centos6-kvm3 ~]# expr 2*2 2*2 [root@centos6-kvm3 ~]# expr 2 * 2 expr: syntax error [root@centos6-kvm3 ~]# expr 2 \* 2 4 ④$[] [root@centos6-kvm3 ~]# echo $[2-3] -1 [root@centos6-kvm3 ~]# echo $[1+3] 4
①bc [root@centos6-kvm3 ~]# bc 1+2 3 2-1 1 [root@centos6-kvm3 ~]# echo 1.1+2| bc 3.1 ②awk [root@centos6-kvm3 ~]# echo 2.1 1.4| awk '{print $1*$2}' 2.94 [root@centos6-kvm3 ~]# echo 2.1 1.4| awk '{print $1-$2}' 0.7
[root@centos6-kvm3 ~]# expr 2 + 3 5 [root@centos6-kvm3 ~]# expr 2 + a expr: non-numeric argument [root@centos6-kvm3 ~]# echo $? 2 [root@centos6-kvm3 ~]# a=2 [root@centos6-kvm3 ~]# expr 2 + $a &>/dev/null [root@centos6-kvm3 ~]# echo $? 0 [root@centos6-kvm3 ~]# a=oldboy [root@centos6-kvm3 ~]# expr 2 + $a &>/dev/null [root@centos6-kvm3 ~]# echo $? 2 [root@centos6-kvm3 ~]# 判断参数是否为整数应用脚本: [root@centos6-kvm3 scripts]# cat judge.sh #!/bin/bash expr 2 + $1 &>/dev/null if [ $? -eq 0 ] then echo "$1 is 整数" else echo "$1 is not 整数" fi [root@centos6-kvm3 scripts]# sh judge.sh 4 4 is 整数 [root@centos6-kvm3 scripts]# sh judge.sh j j is not 整数 [root@centos6-kvm3 scripts]#
[root@centos6-kvm3 scripts]# cat judge1.sh #!/bin/bash expr "$1" : ".*\.txt" &>/dev/null if [ $? -eq 0 ] then echo "$1 is 文本" else echo "$1 is not 文本" fi [root@centos6-kvm3 scripts]# sh judge1.sh old.txt old.txt is 文本 [root@centos6-kvm3 scripts]# sh judge1.sh old.log old.log is not 文本 [root@centos6-kvm3 scripts]#
[root@centos6-kvm3 scripts]# oldboy="i am oldboy" [root@centos6-kvm3 scripts]# echo ${#oldboy} 11 [root@centos6-kvm3 scripts]# expr length "$oldboy" 11 [root@centos6-kvm3 scripts]#
转自:https://www.cnblogs.com/cuiyongchao007/p/12791382.html
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