1.${parameter}
${parameter}是用来处理和(或)扩展变量,${parameter}与$parameter相同,只不过在某些上下文中,使用${parameter}很少会产生混淆。
2.实例
脚本样例:
#!/bin/bash
my_id=${USER}-of-${HOSTNAME}
echo "$my_id"
echo "Old \$PATH = $PATH"
PATH=${PATH}:/opt/bin
echo "New \$PATH = $PATH"
exit 0
结果:
[root@kibana ~]# sh parameter.sh
root-of-kibana
Old $PATH = /usr/lib64/qt-3.3/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin
New $PATH = /usr/lib64/qt-3.3/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin:/opt/bin
[root@kibana ~]#