java - 如何知道环境变量是否设置成功(Mac)

Question

尝试将 JAVA_HOME 环境变量设置为 JDK 的位置。ls -l 'which java' 返回 lrwxr-xr-x 1 root wheel 74 Nov 9 13:31/usr/bin/java ->/System/.../java

所以我假设 /System/Library/Frameworks/JavaVM.framework/Versions/Current/Commands/java 是我的 JDK 的正确位置。所以我应该做的就是编写 export JAVA_HOME=$(/System/.../java)。

这样做后，我得到了大量的输出:

Usage: java [-options] class [args...]
           (to execute a class)
   or  java [-options] -jar jarfile [args...]
           (to execute a jar file)
where options include:
    -d32      use a 32-bit data model if available
    -d64      use a 64-bit data model if available
    -server   to select the "server" VM
                  The default VM is server,
                  because you are running on a server-class machine.


    -cp <class search path of directories and zip/jar files>
    -classpath <class search path of directories and zip/jar files>
                  A : separated list of directories, JAR archives,
                  and ZIP archives to search for class files.
    -D<name>=<value>
                  set a system property
    -verbose:[class|gc|jni]
                  enable verbose output
    -version      print product version and exit
    -version:<value>
                  Warning: this feature is deprecated and will be removed
                  in a future release.
                  require the specified version to run
    -showversion  print product version and continue
    -jre-restrict-search | -no-jre-restrict-search
                  Warning: this feature is deprecated and will be removed
                  in a future release.
                  include/exclude user private JREs in the version search
    -? -help      print this help message
    -X            print help on non-standard options
    -ea[:<packagename>...|:<classname>]
    -enableassertions[:<packagename>...|:<classname>]
                  enable assertions with specified granularity
    -da[:<packagename>...|:<classname>]
    -disableassertions[:<packagename>...|:<classname>]
                  disable assertions with specified granularity
    -esa | -enablesystemassertions
                  enable system assertions
    -dsa | -disablesystemassertions
                  disable system assertions
    -agentlib:<libname>[=<options>]
                  load native agent library <libname>, e.g. -agentlib:hprof
                  see also, -agentlib:jdwp=help and -agentlib:hprof=help
    -agentpath:<pathname>[=<options>]
                  load native agent library by full pathname
    -javaagent:<jarpath>[=<options>]
                  load Java programming language agent, see java.lang.instrument
    -splash:<imagepath>
                  show splash screen with specified image
See http://www.oracle.com/technetwork/java/javase/documentation/index.html for more details.

这看起来像是有关 java 命令使用的某种帮助。我的导出是否成功？ JAVA_HOME 现在是否设置为我的 JDK 的位置？

Answer 1

首先，要使其永久生效，您必须在 Mac 中编辑 ~/.bash_profile 文件。在该文件中，键入上面输入的导出命令。

要检查它是否成功，请在终端中输入 echo $JAVA_HOME 并查看输出。这将告诉您 $JAVA_HOME 当前环境变量的设置。

此外，which 命令仅查找 java 的可执行文件，而不是 SDK 的存储位置。您需要找到您计算机上安装 java 的位置。对我来说，我的是这样的:

导出 JAVA_HOME=$(/usr/libexec/java_home)

当安装新版本的 java 时，这将自动更新。