从shell脚本中的函数返回值(Returning value from called function in a shell script)

从shell脚本中的函数返回值(Returning value from called function in a shell script)

我想从shell脚本中调用的函数返回值。 也许我错过了语法。 我尝试使用全局变量。 但这也不行。 代码是：

lockdir="somedir" test() { retval="" if mkdir "$lockdir" then # directory did not exist, but was created successfully echo >&2 "successfully acquired lock: $lockdir" retval="true" else echo >&2 "cannot acquire lock, giving up on $lockdir" retval="false" fi return retval } retval=test() if [ "$retval" == "true" ] then echo "directory not created" else echo "directory already created" fi

I want to return the value from a function called in a shell script. Perhaps I am missing the syntax. I tried using the global variables. But that is also not working. The code is:

lockdir="somedir" test() { retval="" if mkdir "$lockdir" then # Directory did not exist, but it was created successfully echo >&2 "successfully acquired lock: $lockdir" retval="true" else echo >&2 "cannot acquire lock, giving up on $lockdir" retval="false" fi return retval } retval=test() if [ "$retval" == "true" ] then echo "directory not created" else echo "directory already created" fi

最满意答案

bash函数无法直接返回您想要的字符串。 你可以做三件事情：

回应一个字符串 返回退出状态，这是一个数字，而不是字符串 共享变量

对于其他一些shell也是如此。

以下是每个选项的操作方法：

回声串

lockdir="somedir" testlock(){ retval="" if mkdir "$lockdir" then # directory did not exist, but was created successfully echo >&2 "successfully acquired lock: $lockdir" retval="true" else echo >&2 "cannot acquire lock, giving up on $lockdir" retval="false" fi echo "$retval" } retval=$( testlock ) if [ "$retval" == "true" ] then echo "directory not created" else echo "directory already created" fi

2.退出状态

lockdir="somedir" testlock(){ if mkdir "$lockdir" then # directory did not exist, but was created successfully echo >&2 "successfully acquired lock: $lockdir" retval=0 else echo >&2 "cannot acquire lock, giving up on $lockdir" retval=1 fi return "$retval" } testlock retval=$? if [ "$retval" == 0 ] then echo "directory not created" else echo "directory already created" fi

3.共享变量

lockdir="somedir" retval=-1 testlock(){ if mkdir "$lockdir" then # directory did not exist, but was created successfully echo >&2 "successfully acquired lock: $lockdir" retval=0 else echo >&2 "cannot acquire lock, giving up on $lockdir" retval=1 fi } testlock if [ "$retval" == 0 ] then echo "directory not created" else echo "directory already created" fi

A Bash function can't return a string directly like you want it to. You can do three things:

Echo a string Return an exit status, which is a number, not a string Share a variable

This is also true for some other shells.

Here's how to do each of those options:

1. Echo strings

lockdir="somedir" testlock(){ retval="" if mkdir "$lockdir" then # Directory did not exist, but it was created successfully echo >&2 "successfully acquired lock: $lockdir" retval="true" else echo >&2 "cannot acquire lock, giving up on $lockdir" retval="false" fi echo "$retval" } retval=$( testlock ) if [ "$retval" == "true" ] then echo "directory not created" else echo "directory already created" fi

2. Return exit status

lockdir="somedir" testlock(){ if mkdir "$lockdir" then # Directory did not exist, but was created successfully echo >&2 "successfully acquired lock: $lockdir" retval=0 else echo >&2 "cannot acquire lock, giving up on $lockdir" retval=1 fi return "$retval" } testlock retval=$? if [ "$retval" == 0 ] then echo "directory not created" else echo "directory already created" fi

3. Share variable

lockdir="somedir" retval=-1 testlock(){ if mkdir "$lockdir" then # Directory did not exist, but it was created successfully echo >&2 "successfully acquired lock: $lockdir" retval=0 else echo >&2 "cannot acquire lock, giving up on $lockdir" retval=1 fi } testlock if [ "$retval" == 0 ] then echo "directory not created" else echo "directory already created" fi