AIX本地变量简介及使用
本地变量在用户当前的shell生命周期之内有效，结束当前进程，启动另一个进行，则此变量将无效。设置本地变量的格式：variable-name = value 或者 {valiable-name=value}注意，“=”左右可以有空格，若值有空格，则使用“”包含。下面是实际变量模式----------------------------------------variable-name=value设置实际值到variable-namevariable-name+value如果设置了variable-name，则重置其值variable-name:?value如果未设置variable-name，显示未定义用户错误信息variable-name?value如果未设置variable-name，显示系统错误信息variable-name:=value如果未设置variable-name，则取value值，并将其赋给变量variable-name:-value如果未设置variable-name，则取value值，但不给变量赋值----------------------------------------1.设置变量并显示其值TODAY="Thuesday"echo ${TODAY}ThuesdayMYINFO="my name is $LOGNAME,my home is $HOME"echo ${MYINFO}my name is xxxx,my home is /usr/xxxx2.重置变量：unset variable-nameecho ${MYINFO}my name is xxxx,my home is /usr/xxxxunset MYINFOecho ${MYINFO}3.显示本地所有shell变量：set4.连接变量：echo ${variable-name}${variable-name}echo ${LOGNAME}${HOME}xxxx/usr/xxxx5.检查变量是否被设置命令格式：${variable:-value}意思：如果设置了variable变量的值，则取之，否则使用value，但是不做赋值：variable=value。设置变量值:TODYA="Thuesday"显示变量：echo "today is ${TODAY}"today is Thuesday重置变量:unset TODAY检查变量是否有值：echo "today is ${TODAY:-unknow}"today is unknow查看TODAY的变量值：echo "today is ${TODAY}"today is这里显示TODAY变量现在已经没有包含任何值了。6.下面这个命令，如果变量设置了值，则取之，否则取新值，并给变量赋新值：${variable:=value}设置变量值：SMART_PHONE="iPhone5"查看变量值：echo "a smart phone is ${SMART_PHONE}"a smart phone is iPhone5重置变量值：unset SMART_PHONE检查变量是否有值，若没值，则给其赋值，并显示新值：echo "a smart phone is ${SMART_PHONE:=Meizu MX2}"a smart phone is Meizu MX2查看变量的新值：echo ${SMART_PHONE}Meizu MX27.如果要检查变量是否设置了值，如果有值，则显示值，否则显示一个系统错误信息：echo "${MEIZU_MX2:?} is a better than MI2"[or echo "${MEIZU_MX2?} is a better than MI2"]ksh: MEIZU_MX2: 0403-040 Parameter null or not set.8.如果变量有值，我们可以重新给其赋值：SMART_PHONE="iPhone 4s"echo ${SMART_PHONE}iPhone 4s将变量的值修改了：echo "a smart phone is ${SMART_PHONE+MX2}"a smart phone is MX29.设置只读变量格式：variable-name=valuereadonly variable-name设置变量值：ENAME="Scott"查看变量值：echo "employee 001122 is ${ENAME}"employee 001122 is Scott设置变量只读：readonly ENAME修改变量值：ENAME="Amy"ksh: ENAME: This variable is read only.这里报错，变量ENAME为只读。查看已经设置的只读变量值：readonlyENAME=Scott*当前环境下，只读变量只有刚刚设置的这个ENAME。--the end--