Bash中有TRY CATCH命令吗?

不。

Bash不像在许多编程语言中那样拥有那么多奢侈的东西。

bash中没有try/catch;但是，可以使用&&或||实现类似的行为。

使用| |:

如果command1失败，则command2按如下方式运行

command1 || command2

类似地，使用&&，如果command1成功，command2将运行

try/catch最接近的近似如下

{ # try

    command1 &&
    #save your output

} || { # catch
    # save log for exception 
}

此外，bash还包含一些错误处理机制

set -e

如果任何简单的命令失败，它将停止脚本。

还有为什么不是if…else。它是你最好的朋友。

Bash中有TRY CATCH命令吗?

不。

Bash不像在许多编程语言中那样拥有那么多奢侈的东西。

bash中没有try/catch;但是，可以使用&&或||实现类似的行为。

使用| |:

如果command1失败，则command2按如下方式运行

command1 || command2

类似地，使用&&，如果command1成功，command2将运行

try/catch最接近的近似如下

{ # try

    command1 &&
    #save your output

} || { # catch
    # save log for exception 
}

此外，bash还包含一些错误处理机制

set -e

如果任何简单的命令失败，它将停止脚本。

还有为什么不是if…else。它是你最好的朋友。

我已经在bash中开发了一个几乎完美无缺的try & catch实现，它允许您编写如下代码:

try 
    echo 'Hello'
    false
    echo 'This will not be displayed'

catch 
    echo "Error in $__EXCEPTION_SOURCE__ at line: $__EXCEPTION_LINE__!"

您甚至可以将try-catch块嵌套在它们自己内部!

try {
    echo 'Hello'

    try {
        echo 'Nested Hello'
        false
        echo 'This will not execute'
    } catch {
        echo "Nested Caught (@ $__EXCEPTION_LINE__)"
    }

    false
    echo 'This will not execute too'

} catch {
    echo "Error in $__EXCEPTION_SOURCE__ at line: $__EXCEPTION_LINE__!"
}

代码是bash样板文件/框架的一部分。它进一步扩展了try & catch的思想，例如使用回溯和异常进行错误处理(以及其他一些不错的特性)。

下面是负责try & catch的代码:

set -o pipefail
shopt -s expand_aliases
declare -ig __oo__insideTryCatch=0

# if try-catch is nested, then set +e before so the parent handler doesn't catch us
alias try="[[ \$__oo__insideTryCatch -gt 0 ]] && set +e;
           __oo__insideTryCatch+=1; ( set -e;
           trap \"Exception.Capture \${LINENO}; \" ERR;"
alias catch=" ); Exception.Extract \$? || "

Exception.Capture() {
    local script="${BASH_SOURCE[1]#./}"

    if [[ ! -f /tmp/stored_exception_source ]]; then
        echo "$script" > /tmp/stored_exception_source
    fi
    if [[ ! -f /tmp/stored_exception_line ]]; then
        echo "$1" > /tmp/stored_exception_line
    fi
    return 0
}

Exception.Extract() {
    if [[ $__oo__insideTryCatch -gt 1 ]]
    then
        set -e
    fi

    __oo__insideTryCatch+=-1

    __EXCEPTION_CATCH__=( $(Exception.GetLastException) )

    local retVal=$1
    if [[ $retVal -gt 0 ]]
    then
        # BACKWARDS COMPATIBILE WAY:
        # export __EXCEPTION_SOURCE__="${__EXCEPTION_CATCH__[(${#__EXCEPTION_CATCH__[@]}-1)]}"
        # export __EXCEPTION_LINE__="${__EXCEPTION_CATCH__[(${#__EXCEPTION_CATCH__[@]}-2)]}"
        export __EXCEPTION_SOURCE__="${__EXCEPTION_CATCH__[-1]}"
        export __EXCEPTION_LINE__="${__EXCEPTION_CATCH__[-2]}"
        export __EXCEPTION__="${__EXCEPTION_CATCH__[@]:0:(${#__EXCEPTION_CATCH__[@]} - 2)}"
        return 1 # so that we may continue with a "catch"
    fi
}

Exception.GetLastException() {
    if [[ -f /tmp/stored_exception ]] && [[ -f /tmp/stored_exception_line ]] && [[ -f /tmp/stored_exception_source ]]
    then
        cat /tmp/stored_exception
        cat /tmp/stored_exception_line
        cat /tmp/stored_exception_source
    else
        echo -e " \n${BASH_LINENO[1]}\n${BASH_SOURCE[2]#./}"
    fi

    rm -f /tmp/stored_exception /tmp/stored_exception_line /tmp/stored_exception_source
    return 0
}

你可以自由使用，分叉和贡献——它在GitHub上。

Bash不会在检测到错误状态时中止正在运行的执行(除非您设置了-e标志)。提供try/catch的编程语言这样做是为了抑制由于这种特殊情况而产生的“保释”(因此通常称为“异常”)。

相反，在bash中，只有有问题的命令将退出，退出码大于0，表示错误状态。当然，您可以检查这一点，但由于没有任何自动保释，因此try/catch没有意义。它只是缺乏背景。

然而，你可以通过使用子壳来模拟一个保释，它可以在你决定的点终止:

(
  echo "Do one thing"
  echo "Do another thing"
  if some_condition
  then
    exit 3  # <-- this is our simulated bailing out
  fi
  echo "Do yet another thing"
  echo "And do a last thing"
)   # <-- here we arrive after the simulated bailing out, and $? will be 3 (exit code)
if [ $? = 3 ]
then
  echo "Bail out detected"
fi

而不是some_condition的if你也可以尝试一个命令，如果它失败(退出码大于0)，保释:

(
  echo "Do one thing"
  echo "Do another thing"
  some_command || exit 3
  echo "Do yet another thing"
  echo "And do a last thing"
)
...

不幸的是，使用这种技术只能使用255个不同的退出码(1..255)，而且不能使用像样的异常对象。

如果你需要更多的信息来传递模拟异常，你可以使用subshell的stdout，但这有点复杂，可能是另一个问题;-)

使用上面提到的-e标志，你甚至可以剥离显式的退出语句:

(
  set -e
  echo "Do one thing"
  echo "Do another thing"
  some_command
  echo "Do yet another thing"
  echo "And do a last thing"
)
...

你可以:

#!/bin/bash
if <command> ; then # TRY
    <do-whatever-you-want>
else # CATCH
    echo 'Exception'
    <do-whatever-you-want>
fi

根据我在这里找到的一些答案，我为自己的项目制作了一个小的帮助文件:

trycatch.sh

#!/bin/bash

function try()
{
    [[ $- = *e* ]]; SAVED_OPT_E=$?
    set +e
}

function throw()
{
    exit $1
}

function catch()
{
    export ex_code=$?
    (( $SAVED_OPT_E )) && set +e
    return $ex_code
}

function throwErrors()
{
    set -e
}

function ignoreErrors()
{
    set +e
}

下面是它在使用中的示例:

#!/bin/bash
export AnException=100
export AnotherException=101

# start with a try
try
(   # open a subshell !!!
    echo "do something"
    [ someErrorCondition ] && throw $AnException

    echo "do something more"
    executeCommandThatMightFail || throw $AnotherException

    throwErrors # automaticatly end the try block, if command-result is non-null
    echo "now on to something completely different"
    executeCommandThatMightFail

    echo "it's a wonder we came so far"
    executeCommandThatFailsForSure || true # ignore a single failing command

    ignoreErrors # ignore failures of commands until further notice
    executeCommand1ThatFailsForSure
    local result = $(executeCommand2ThatFailsForSure)
    [ result != "expected error" ] && throw $AnException # ok, if it's not an expected error, we want to bail out!
    executeCommand3ThatFailsForSure

    # make sure to clear $ex_code, otherwise catch * will run
    # echo "finished" does the trick for this example
    echo "finished"
)
# directly after closing the subshell you need to connect a group to the catch using ||
catch || {
    # now you can handle
    case $ex_code in
        $AnException)
            echo "AnException was thrown"
        ;;
        $AnotherException)
            echo "AnotherException was thrown"
        ;;
        *)
            echo "An unexpected exception was thrown"
            throw $ex_code # you can rethrow the "exception" causing the script to exit if not caught
        ;;
    esac
}