shell小结(3)

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set:查看本地变量
env:查看环境变量
alias:查看已经定义的别名
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JDK的检查：
	if [ "x$JAVAHOME" = "x" ]; then
        echo "JAVAHOME环境变量未设置"
        exit 1
    fi
    if [ -x $JAVAHOME/bin/java ]; then
        printf ""
    else
        echo "错误的JAVAHOME环境变量设置。$JAVAHOME/bin/java 程序不存在。"
        echo "请重新指定JDK安装路径。"
        exit 2
    fi
    if [ -x $JAVAHOME/bin/javac ]; then
        printf ""
    else
        echo "您指定的JAVAHOME环境变量为$JAVAHOME"
        echo "该位置下找不到javac命令。可能您安装的是JRE而不是JDK。请检查。"
        exit 6
    fi
    R="`$JAVAHOME/bin/java -version 2>&1`"
    if [ "x`echo $R | grep 'Could not reserve enough space for object heap'`" != "x" ]; then
        echo "$JAVAHOME/bin/java运行出错：内存不足无法启动。请检查系统资源占用情况。"
        echo $R
        exit 3
    fi
    if [ "x`echo $R | grep Error`" != "x" ]; then
        echo "$JAVAHOME/bin/java运行出错。请检查。"
        echo $R
        exit 4
    fi
    if [ "x`echo $R | grep '\"1\.5'`" = "x" ]; then
        echo "$JAVAHOME/bin/java 的版本不是1.5。"
        echo "请设置环境变量JAVAHOME指向正确版本的JDK安装路径。"
        exit 5
    fi
    cd "`/usr/bin/dirname $0`/.."
    if [ "x$MMS_HOME" = "x" ]; then
        MMS_HOME=`/bin/pwd`
        export MMS_HOME
    fi
    cd $MMS_HOME
    MMS_HOME=`/bin/pwd`
    CLASSPATH=`ls -1 $WADHOME/bin/*.jar |/usr/bin/tr '\n' ':'`; export CLASSPATH
}

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readonly:
定义的变量是只读的，相当于final
#!/bin/bash

readonly name=xuxu

echo $name

name=xuxux

echo $name

但要注意：
	typeset readonly name=xuxu时，这时的readonly会失效！


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#转到上层目录
cd `dirname $0`/..

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比较运算：

#!/bin/bash

#可以比较数字
if [[ 1 <= 2 ]];then
	echo 'ok'
fi

#也可以比较字符串
if [[ "a" < "b" ]];then
	echo 'ok'
fi

#下面这两种方式不要使用
#!/bin/bash
	
if [  1 ]  ; then
	echo 'oookkkk'
fi  

if [ true ]; then
	echo 'ook'
fi


//另一种比较的写法，据点是：只能比较整数
#!/bin/bash

a=1
b=2

//当然也可以((a<=b))
if (($a<=$b));then
	echo 'ok'
fi

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