从Shell脚本中的被调用函数返回值

我想从外壳程序脚本中调用的函数返回值。也许我缺少语法。我尝试使用全局变量。但这也不起作用。代码是：

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

Bash函数无法像您想要的那样直接返回字符串。您可以做三件事：

1. 回声字符串
2. 返回退出状态，它是一个数字，而不是字符串
3. 共享变量

对于其他一些shell也是如此。

这是每个选项的操作方法：

1.回声弦

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.返回退出状态

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.分享变量

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

你工作太辛苦了。您的整个脚本应为：

if mkdir "$lockdir" 2> /dev/null; then 
  echo lock acquired
else
  echo could not acquire lock >&2
fi

但这甚至太冗长了。我会编码：

mkdir "$lockdir" || exit 1

但是产生的错误消息有点模糊。

如果这只是一个对/错的测试，那么请发挥return 0成功和return 1失败的作用。测试将是：

if function_name; then
  do something
else
  error condition
fi

我认为为succ / 1返回0表示失败（格伦·杰克曼），而olibre清晰而有说服力的答案说明了一切。仅提及一种针对结果不是二进制的情况的“组合”方法，您宁愿设置变量而不是“回显”结果（例如，如果您的函数还假设是回显某些内容，则该方法将不行）。然后怎样呢？（下面是《伯恩·壳》）

# Syntax _w (wrapReturn)
# arg1 : method to wrap
# arg2 : variable to set
_w(){
eval $1
read $2 <<EOF
$?
EOF
eval $2=\$$2
}

如（是的，示例有点愚蠢，这只是一个示例。）

getDay(){
  d=`date '+%d'`
  [ $d -gt 255 ] && echo "Oh no a return value is 0-255!" && BAIL=0 # this will of course never happen, it's just to clarify the nature of returns
  return $d
}

dayzToSalary(){
  daysLeft=0
  if [ $1 -lt 26 ]; then 
      daysLeft=`expr 25 - $1`
  else
     lastDayInMonth=`date -d "`date +%Y%m01` +1 month -1 day" +%d`
     rest=`expr $lastDayInMonth - 25`
     daysLeft=`expr 25 + $rest`
  fi
  echo "Mate, it's another $daysLeft days.."
}

# main
_w getDay DAY # call getDay, save the result in the DAY variable
dayzToSalary $DAY

如果您有一些参数要传递给函数，并希望返回一个值。在这里，我将“ 12345”作为参数传递给函数，并在处理完返回变量XYZ后将其分配给VALUE

#!/bin/bash
getValue()
{
    ABC=$1
    XYZ="something"$ABC
    echo $XYZ
}


VALUE=$( getValue "12345" )
echo $VALUE

输出：

something12345