Shell 脚本的条件测试与比较 {mtitle title="条件测试常用语法"/}Shell脚本条件测试语法说明test利用test命令进行条件测试[]通过[]进行条件测试[[]]通过[[]]进行条件测试(())通过(())进行条件测试test语法test -f file && echo true || echo false #存在输出true，不存在输出false[]语法[ -f /tmp/123.txt ] && echo 1 || echo 0 #存在输出1，不存在输出0[[]]语法[[ -f /tmp/123.txt ]] &&echo 1 || echo 0 #存在输出1，不存在输出0文件测试表达式{mtitle title="常用的文件测试符"/}文件测试操作符说明-d 文件文件存在且为目录为真，及测试表达式成立-f 文件文件存在且为普通文件为真，及测试表达式成立-e 文件文件存在即为真，则表达式成立，不区别文件和目录-r 文件文件存在且可读为真，及测试表达式成立-w 文件文件存在且可写为真，及测试表达式成立-x 文件文件存在且可执行为真，及测试表达式成立-s 文件文件存在且文件大小不为0为真，及测试表达式成立-L 文件文件存在且为链接文件为真，及测试表达式成立f1 -nt f2文件f1比文件f2新则为真，即表达式成立，根据文件的修改时间来计算f1 -ot f2文件f1比文件f2旧则为真，即表达式成立，根据文件的修改时间来计算字符串测试表达式{mtitle title="字符串测试符"/}字符串测试符说明-n "字符串"若字符串不为“0”，则为真，即表达式成立-z "字符串"若字符串为“0”，则为真，即表达式成立"串1" = "串2"若字符串1等于字符串2，则为真，即表达式成立"串1" != "串2"若字符串1不等于字符串2，则为真，即表达式成立整数二次元比较符在[]以及test中使用的比较符在(())和[[]]中使用的比较符说明-eq==或者=相等-ne!=不相等-gt>大于-ge>=大于等于-lt<小于-le<=小于等于root@cs:/server/scripts# a1=98;a2=64 root@cs:/server/scripts# [ "$a1" -eq "$a2" ] && echo 1 || echo 00 root@cs:/server/scripts# [ "$a1" -ne "$a2" ] && echo 1 || echo 01 root@cs:/server/scripts# [ "$a1" -gt "$a2" ] && echo 1 || echo 01 root@cs:/server/scripts# [ "$a1" -lt "$a2" ] && echo 1 || echo 00逻辑操作符{mtitle title="逻辑操作符"/}在[]和test中使用的操作符在[[]]和(())中使用的操作符说明-a&&and,与，两端为真，则结果为真-o双竖线or,或，两端一个为真，则结果为真!!not,非，两端相反，则结果为真使用-a和&&时当左边为真，右边为假时，结果为假。当左边为假，右边为真时，结果为假。当左边为真，右边为真时，结果为真。当左边为假，右边为假时，结果为假。root@cs:/server/scripts# [ 5 -eq 6 -a 7 -ne 5 ] && echo 1 || echo 0 #5等于7？假 7不等于5？ 真 结果为假 输出0 0 root@cs:/server/scripts# [ 5 -lt 6 -a 7 -ne 5 ] && echo 1 || echo 0 #5<7？真 7不等于5？ 真 结果为真 输出1 1使用-o 或 双竖线时当左边为真，右边为假时，结果为真。当左边为假，右边为真时，结果为真。当左边为真，右边为真时，结果为真。当左边为假，右边为假时，结果为假。root@cs:/server/scripts# [ 5 -lt 6 -o 7 -ne 5 ] && echo 1 || echo 0 1 root@cs:/server/scripts# [ 5 -eq 6 -o 7 -ne 5 ] && echo 1 || echo 0 1 root@cs:/server/scripts# [ 5 -gt 6 -o 7 -lt 5 ] && echo 1 || echo 0 0root@cs:/server/scripts# f1=/etc/rc.local;f2=/etc/services root@cs:/server/scripts# echo -ne "$f1 $f2\n" /etc/rc.local /etc/services root@cs:/server/scripts# [ -f "$f1" -a -f "$f2" ] && echo 1 || echo 0 1 root@cs:/server/scripts# [ -f "$f1" -a -f "$f222" ] && echo 1 || echo 0 0 root@cs:/server/scripts# [ -f "$f1" -o -f "$f222" ] && echo 1 || echo 0 1 root@cs:/server/scripts# [ -f "$f111" -o -f "$f222" ] && echo 1 || echo 0 0 root@cs:/server/scripts# [ -f "$f1" ] && [ -f "$f2" ] && echo 1 || echo 0 1 root@cs:/server/scripts# a="test";b="echo" root@cs:/server/scripts# echo -eq "$a $b\n" -eq test echo\n root@cs:/server/scripts# echo -ne "$a $b\n" test echo root@cs:/server/scripts# [[ ! -n "$a" && "$a" = "$b" ]] && echo 0 || echo 1 1 root@cs:/server/scripts# [[ -z "$a" && "$a" != "$b" ]] && echo 0 || echo 1 1 root@cs:/server/scripts# [[ -z "$a" || "$a" != "$b" ]] && echo 0 || echo 1 0 root@cs:/server/scripts# [[ -z "$a" -o "$a" != "$b" ]] && echo 0 || echo 1 -bash: syntax error in conditional expression -bash: syntax error near `-o'root@cs:/server/scripts# m=21;n=38 root@cs:/server/scripts# [ $m -gt 20 -a $n -lt 30 ] && echo 1 || echo 0 0 root@cs:/server/scripts# [ $m -gt 20 ] && [ $n -lt 30 ] && echo 1 || echo 0 0 root@cs:/server/scripts# [ $m -gt 20 ] || [ $n -lt 30 ] && echo 1 || echo 0 1逻辑操作符输入或通过命令行输入一个数字，如果传入的数字等于1，就打印1，输入2，就打印2，输入其他数字就退出程序root@cs:/server/scripts# cat ljczf.sh #!/bin/bash read -p "please input num:" num [ "$num" = "1" ] && { echo 1 exit 0 } [ "$num" = "2" ] && { echo 2 exit 0 } [ "$num" != "1" -a "$num" != "2" ] && { echo error exit 1 }传参方式 root@cs:/server/scripts# cat ljczf1.sh #!/bin/bash echo "plase input num" num=$1 [ "$num" = "1" ] && { echo 1 exit 0 } [ "$num" = "2" ] && { echo 2 exit 0 } [ "$num" != "1" -a "$num" != "2" ] && { echo error exit 1 }比较两个整数的大小root@cs:/server/scripts# cat int.sh #!/bin/bash read -p "pls input two num:" num1 num2 [ -z "$num1" -a -z "$num2" ] && { echo error exit 1 } expr $num1 + 1 &>/dev/null RETVAL_n1=$? expr $num2 + 1 &>/dev/null RETVAL_n2=$? [ $RETVAL_n1 -eq 0 -a $RETVAL_n2 -eq 0 ] || { echo "pls input two num again" exit 2 } [ $num1 -lt $num2 ] && { echo "$num1 < $num2" exit 0 } [ $num1 -eq $num2 ] && { echo "$num1 = $num2" exit 0 } [ $num1 -gt $num2 ] && { echo "$num1 > $num2" } root@cs:/server/scripts# sh int.sh pls input two num:6 3 6 > 3 root@cs:/server/scripts# sh int.sh pls input two num:3 6 3 < 6 root@cs:/server/scripts# sh int.sh pls input two num:6 6 6 = 6 root@cs:/server/scripts# sh int.sh pls input two num:dd ff pls input two num again root@cs:/server/scripts# cat int1.sh #!/bin/bash num1=$1 num2=$2 [ $# -ne 2 ] && { echo "USAGE:$0 num1 num2" exit 1 } expr $num1 + 1 &>/dev/null RETVAL_n1=$? expr $num2 + 1 &>/dev/null RETVAL_n2=$? [ $RETVAL_n1 -eq 0 -a $RETVAL_n2 -eq 0 ] || { echo "pls input two num again" exit 2 } [ $num1 -lt $num2 ] && { echo "$num1 < $num2" exit 0 } [ $num1 -eq $num2 ] && { echo "$num1 = $num2" exit 0 } [ $num1 -gt $num2 ] && { echo "$num1 > $num2" } root@cs:/server/scripts# sh int1.sh 6 3 6 > 3 root@cs:/server/scripts# sh int1.sh 3 6 3 < 6 root@cs:/server/scripts# sh int1.sh 3 3 3 = 3 root@cs:/server/scripts# sh int1.sh dd ff pls input two num again

Shell:变量数值计算(下) bc 命令用法如果没有安装bc,用下面命令进行安装centos systemctl intall -y bcUnbunt apt-get install -y bcroot@cs:/server/scripts# echo 3+5|bc 8 root@cs:/server/scripts# echo 3-5|bc -2 root@cs:/server/scripts# echo 3.6-5.2|bc -1.6 root@cs:/server/scripts# echo 3.6*5.2|bc 18.7 root@cs:/server/scripts# echo "scale=2;355/113"|bc 3.14 root@cs:/server/scripts# echo "scale=6;355/113"|bc 3.141592计算1-10的结果root@cs:/server/scripts# echo `seq -s "+" 10`=`seq -s "+" 10|bc` 1+2+3+4+5+6+7+8+9+10=55 root@cs:/server/scripts# echo `seq -s "+" 10`=$((`seq -s "+" 10`)) 1+2+3+4+5+6+7+8+9+10=55 root@cs:/server/scripts# echo `seq -s '+' 10`=$(echo $[`seq -s "+" 10`]) 1+2+3+4+5+6+7+8+9+10=55 awk实现计算root@cs:/server/scripts# echo "5.3 6.9"|awk '{print ($1+$2)}' 12.2 root@cs:/server/scripts# echo "5.3 6.9"|awk '{print ($1-$2)}' -1.6 root@cs:/server/scripts# echo "5.3 6.9"|awk '{print ($1*$2)}' 36.57 root@cs:/server/scripts# echo "5.3 6.9"|awk '{print ($1/$2)}' 0.768116$[]实现运算root@cs:/server/scripts# i=8 root@cs:/server/scripts# i=$[i+6] root@cs:/server/scripts# echo $i 14 root@cs:/server/scripts# echo $[i-5] 9 root@cs:/server/scripts# echo $[i*5] 70 root@cs:/server/scripts# echo $[i**5] 537824 root@cs:/server/scripts# echo $[i/5] 2 root@cs:/server/scripts# echo $[i%5] 4基于Shell 变量输入read 命令的运算实践root@cs:/server/scripts# cat test3.sh #!/bin.bash read -p "please input two:" a b echo "a+b=$(($a+$b))" echo "a-b=$(($a-$b))" echo "a*b=$(($a*$b))" echo "a/b=$(($a/$b))" echo "a**b=$(($a**$b))" echo "a%b=$(($a%$b))" echo "a++:$((a++))" echo "a=$a" echo "++a:$((++a))" echo "a=$a" echo "b--:$((--b))" echo "b=$b" echo "--b:$((--b))" echo "b=$b"执行结果root@cs:/server/scripts# sh test3.sh please input two:2 2 a+b=4 a-b=0 a*b=4 a/b=1 a**b=4 a%b=0 a++:2 a=3 ++a:4 a=4 b--:1 b=1 --b:0 b=0完善的代码root@cs:/server/scripts# cat test3.sh #!/bin.bash read -t 15 -p "please input two:" a b [ ${#a} -le 0 ]&&{ echo "the first num is null" exit 1 } [ ${#b} -le 0 ]&&{ echo "the first num is null" exit 1 } expr $a + 1 &>/dev/null REVTAL_A=$? expr $b + 1 &>/dev/null REVTAL_B=$? if [ $REVTAL_A -ne 0 -o $REVTAL_B -ne 0 ];then echo "one of the num is not num,pls input again." exit 1 fi echo "a+b=$(($a+$b))" echo "a-b=$(($a-$b))" echo "a*b=$(($a*$b))" echo "a/b=$(($a/$b))" echo "a**b=$(($a**$b))" echo "a%b=$(($a%$b))" echo "a++:$((a++))" echo "a=$a" echo "++a:$((++a))" echo "a=$a" echo "b--:$((--b))" echo "b=$b" echo "--b:$((--b))" echo "b=$b"运算结果root@cs:/server/scripts# sh test3.sh please input two:12 12 a+b=24 a-b=0 a*b=144 a/b=1 a**b=8916100448256 a%b=0 a++:12 a=13 ++a:14 a=14 b--:11 b=11 --b:10 b=10用传参方式进行运算