bash Mac echo $JAVA_HOME 返回空白
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Mac echo $JAVA_HOME return blank
提问by user1034127
I don't know why echo $JAVA_HOME return blank
我不知道为什么 echo $JAVA_HOME 返回空白
Abdelmajids-iMac:~ majid$ vi .profile
Abdelmajids-iMac:~ majid$ vi .profile
export PATH=/usr/local/bin:(...)
[[ -s "$HOME/.rvm/scripts/rvm" ]] && source "$HOME/.rvm/scripts/rvm" # Load
RVM into a shell session *as a function*
export JAVA_HOME=$(/usr/libexec/java_home)
~
~
Abdelmajids-iMac:~ majid$ /usr/libexec/java_home
/Library/Java/JavaVirtualMachines/jdk1.8.0_151.jdk/Contents/Home
Abdelmajids-iMac:~ majid$ vi .bash_profile
Abdelmajids-iMac:~ majid$ source .bash_profile
-bash: .bash_profile: line 1: syntax error near unexpected token `('
-bash: .bash_profile: line 1: `export PATH=/usr/local/bin:(...)'
Abdelmajids-iMac:~ majid$ echo $JAVA_HOME
Abdelmajids-iMac:~ majid$
回答by pradosh nair
Statement export JAVA_HOME=$(/usr/libexec/java_home)seems incorrect; bash would have evaluated the information within $() and returned a blank.
陈述export JAVA_HOME=$(/usr/libexec/java_home)似乎不正确；bash 会评估 $() 中的信息并返回一个空白。
It should just be export JAVA_HOME=$(echo /usr/libexec/java_home)or export JAVA_HOME=/usr/libexec/java_home.
它应该只是export JAVA_HOME=$(echo /usr/libexec/java_home)或export JAVA_HOME=/usr/libexec/java_home。
The usage of $() is discussed in this link. Difference between ${} and $() in bash scripting.
此链接中讨论了 $() 的用法。bash 脚本中 ${} 和 $() 之间的区别。
回答by jprism
$(str) where str should be a command. In your case, $(/usr/libexec/java_home) will return nothing. Just use
$(str) 其中 str 应该是一个命令。在您的情况下， $(/usr/libexec/java_home) 将不返回任何内容。只需使用
export JAVA_HOME=/usr/libexec/java_home
