Linux shell 字符串常用操作
# var=oldboy123# echo ${var}
oldboy123
# echo ${#var}
9
#例如：
#以下判断用read输入一个值，如果长度为0，则值为空，否则打印出变量的值
# cat if4.sh
#!/bin/bash
read -p "pls input a num: " a
if [ ${#a} -eq 0 ]
then
echo "a is null,pls input a nums again!"
exit 1
else
echo "a=$a"
fi
#测试
# sh if4.sh
pls input a num:
a is null,pls input a nums again!
# sh if4.sh
pls input a num: d
a=d
# sh if4.sh
pls input a num: 123
a=123
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