我正在写一个shell脚本,需要检查终端应用程序是否已安装。我想使用TRY/CATCH命令来做到这一点,除非有更整洁的方法。
当前回答
正如大家所说,bash没有适当的语言支持的try/catch语法。您可以使用-e参数启动bash,或者在脚本中使用set -e来中止整个bash进程,如果任何命令有非零退出码的话。(你也可以设置+e来临时允许失败的命令。)
因此,模拟try/catch块的一种技术是在启用-e的情况下启动子进程来完成工作。然后在主进程中,检查子进程的返回码。
Bash支持heredoc字符串,因此不需要编写两个单独的文件来处理这个问题。在下面的示例中,TRY heredoc将在单独的bash实例中运行,并启用了-e,因此如果任何命令返回非零退出码,子进程将崩溃。然后,回到主进程,我们可以检查返回代码以处理一个catch块。
#!/bin/bash
set +e
bash -e <<TRY
echo hello
cd /does/not/exist
echo world
TRY
if [ $? -ne 0 ]; then
echo caught exception
fi
它不是一个适当的语言支持的try/catch块,但它可能会为您带来类似的体验。
其他回答
假设终端应用名为'app'(你希望它在你的$PATH中):
if [[ ! `which app` ]]; then
# run code if app not installed
else
# run code if app is installed
fi
借用肖恩·梅奥的回答,你可以这样做
function check {
EXITCODE=$?
if [ "$EXITCODE" -ne "0" ]; then
#this is the catch part
echo "uh oh"
exit $EXITCODE
fi
}
YOUR COMMAND HERE
check
YOUR COMMAND HERE
check
YOUR COMMAND HERE
check
YOUR COMMAND HERE
check
效果很好
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 $ex_code # you can rethrow the "exception" causing the script to exit if not caught
;;
esac
}
Bash中有TRY CATCH命令吗?
不。
Bash不像在许多编程语言中那样拥有那么多奢侈的东西。
bash中没有try/catch;但是,可以使用&&或||实现类似的行为。
使用| |:
如果command1失败,则command2按如下方式运行
command1 || command2
类似地,使用&&,如果command1成功,command2将运行
try/catch最接近的近似如下
{ # try
command1 &&
#save your output
} || { # catch
# save log for exception
}
此外,bash还包含一些错误处理机制
set -e
如果任何简单的命令失败,它将停止脚本。
还有为什么不是if…else。它是你最好的朋友。
我使用的方法是这样的:
YOUR COMMAND HERE
EXITCODE=$?
if [ "$EXITCODE" -ne "0" ]; then
#this is the catch part
echo "uh oh"
exit $EXITCODE
fi
这只是检查命令的退出码,并将其与零进行比较 (表示命令运行成功)