如何检查$?在unix shell脚本中不等于零?
我有一个脚本,它使用test命令检查如何检查$?在unix shell脚本中不等于零?,shell,unix,Shell,Unix,我有一个脚本,它使用test命令检查$?(上次执行命令的返回代码)是否不等于零。代码如下:- $?是最后执行的命令的退出状态 if (test $? -ne 0) then //statements// fi 但是,这种验证方法不适用于字符串,因为get语法错误。请建议一个合适的替代方案 首先将其放入变量中,然后尝试测试它,如下所示 ret=$? if [ $ret -ne 0 ]; then echo "In If" else echo "In Else" f
$?
(上次执行命令的返回代码)是否不等于零。代码如下:-
$?
是最后执行的命令的退出状态
if (test $? -ne 0)
then
//statements//
fi
但是,这种验证方法不适用于字符串,因为get语法错误。请建议一个合适的替代方案 首先将其放入变量中,然后尝试测试它,如下所示
ret=$?
if [ $ret -ne 0 ]; then
echo "In If"
else
echo "In Else"
fi
这应该会有所帮助
编辑:如果上述操作没有按预期进行,则可能是您没有在正确的位置使用
$?
它必须是命令后的下一行,您需要捕捉返回状态。即使在目标和您捕获其返回状态之间有任何其他单个命令,您也将检索此中间命令的返回状态,而不是您期望的状态。我不知道您是如何在$?
中获得字符串的,但您可以:
if [[ "x$?" == "x0" ]]; then
echo good
fi
a=${?}
如果[${a}-ne 0];然后呼应“做点什么”;fi
使用您想要使用的任何命令,而不是
echo“do something”
命令这是针对类似问题提出的解决方案
exit_status () {
if [ $? = 0 ]
then
true
else
false
fi
}
用法:
do-command exit_status && echo "worked" || echo "didnt work"
在执行脚本后尝试以下操作:
if [ $? -ne 0 ];
then
//statements//
fi
您不需要测试
$?
是否不是0
。shell提供了&&
和|
,因此您可以轻松地根据该测试的隐式结果进行分支:
some_command && {
# executes this block of code,
# if some_command would result in: $? -eq 0
} || {
# executes this block of code,
# if some_command would result in: $? -ne 0
}
根据需要,可以删除任一分支。因此,如果您只想测试失败(即,$?-ne 0
):
但是,您在问题中提供的代码可以正常工作。我对你的语法错误感到困惑&我断定$?
是一个字符串。很可能是问题中没有提供导致语法错误的错误代码。这一点尤其明显,因为您声称其他人的解决方案也不起作用。当这种情况发生时,你必须重新评估你的假设
注意:如果大括号内的代码返回错误,上面的代码可能会给出令人困惑的结果。在这种情况下,只需使用if命令,如下所示:
if some_command; then
# executes this block of code,
# if some_command would result in: $? -eq 0
else
# executes this block of code,
# if some_command would result in: $? -ne 0
fi
将set-o pipefail放在任何脚本的开头,以返回任何失败 如果你这样做了,测试失败了,但发球台没有。默认情况下$?只需执行最后一个命令success,在本例中为“tee”命令
我编写了一些代码,这些代码可能有助于了解返回值与返回字符串的工作方式。也许有更好的方法,但这是我通过测试发现的
#!/bin/sh
#
# ro
#
pass(){
echo passed
return 0; # no errors
}
fail(){
echo failed
return 1; # has an error
}
t(){
echo true, has error
}
f(){
echo false, no error
}
dv=$(printf "%60s"); dv=${dv// /-}
echo return code good for one use, not available for echo
echo $dv
pass
[ $? -gt 0 ] && t || f
echo "function pass: \$? $?" ' return value is gone'
echo
fail
[ $? -gt 0 ] && t || f
echo "function fail: \$? $?" ' return value is gone'
echo
echo save return code to var k for continued usage
echo $dv
pass
k=$?
[ $k -gt 0 ] && t || f
echo "function pass: \$k $k"
echo
fail
k=$?
[ $k -gt 0 ] && t || f
echo "function fail: \$k $k"
echo
# direct evaluation of the return value
# note that (...) and $(...) executes in a subshell
# with return value to calling shell
# ((...)) is for math/string evaluation
echo direct evaluations of the return value:
echo ' by if (pass) and if (fail)'
echo $dv
if (pass); then
echo pass has no errors
else
echo pass has errors
fi
if (fail); then
echo fail has no errors
else
echo fail has errors
fi
# this code results in error because of returned string (stdout)
# but comment out the echo statements in pass/fail functions and this code succeeds
echo
echo ' by if $(pass) and if $(fail) ..this succeeds if no echo to stdout from function'
echo $dv
if $(pass); then
echo pass has no errors
else
echo pass has errors
fi
if $(fail); then
echo fail has no errors
else
echo fail has errors
fi
echo
echo ' by if ((pass)) and if ((fail)) ..this always fails'
echo $dv
if ((pass)); then
echo pass has no errors
else
echo pass has errors
fi
if ((fail)); then
echo fail has no errors
else
echo fail has errors
fi
echo
s=$(pass)
r=$?
echo pass, "s: $s , r: $r"
s=$(fail)
r=$?
echo fail, "s: $s , r: $r"
在您的示例中,$?实际上是数字,但由于您使用了方括号,即隐含的“test”命令,因此出现语法错误,而不是因为退出代码是字符串。谢谢…那么您建议我应该尝试什么?请参阅下面的答案,并注意方括号而不是圆括号的使用…我尝试了。。。在我的情况下不起作用!!还有其他建议吗please@user1466466-你能详细说明一下吗?您确定
$?
正在返回您期望的结果吗?试着用这个例子来确认一下,这对我很有用。我通常是乐观的,所以我做的是[$ret-eq 0]
,但这是一个品味的问题。@user1466466我声称它应该有效。你能提供证据证明它不存在吗?换句话说,永远不要只说“它不起作用”。请告诉我们该命令做了什么,以及您希望它做什么。@user1466466请注意所有空格都很重要。例如,[和$ret之间有一个空格,以此类推。我尝试了它…它无法检查条件!!请[…]]
在用户的shell中可能没有任何其他建议。一个更简单的选择是这样定义它:退出状态(){test$?-eq 0;}
。在您的示例中,您可以完全取消无关的exit_status函数,并执行:do命令和&echo“已工作”| | echo“未工作”
。或者您也可以这样做:“$?-eq 0”表示执行的某些_命令没有错误,“$?-ne 0”有错误???@happy,是的,基本正确:$?-eq 0
表示最后一个命令退出时状态代码为0
(成功)。$?-ne 0
表示最后一个命令退出时状态代码为非零(通常是由于错误).我已经在类似的UC中从管道切换到if块,因为它想在出错的情况下退出脚本。()谢谢你!太好了!
if [ $? -ne 0 ];
then
//statements//
fi
some_command && {
# executes this block of code,
# if some_command would result in: $? -eq 0
} || {
# executes this block of code,
# if some_command would result in: $? -ne 0
}
some_command_returning_nonzero || {
# executes this block of code when: $? -ne 0
# and nothing if the command succeeds: $? -eq 0
}
if some_command; then
# executes this block of code,
# if some_command would result in: $? -eq 0
else
# executes this block of code,
# if some_command would result in: $? -ne 0
fi
test | tee /tmp/dump
[ $? -ne 0 ] && echo "failed"
#!/bin/sh
#
# ro
#
pass(){
echo passed
return 0; # no errors
}
fail(){
echo failed
return 1; # has an error
}
t(){
echo true, has error
}
f(){
echo false, no error
}
dv=$(printf "%60s"); dv=${dv// /-}
echo return code good for one use, not available for echo
echo $dv
pass
[ $? -gt 0 ] && t || f
echo "function pass: \$? $?" ' return value is gone'
echo
fail
[ $? -gt 0 ] && t || f
echo "function fail: \$? $?" ' return value is gone'
echo
echo save return code to var k for continued usage
echo $dv
pass
k=$?
[ $k -gt 0 ] && t || f
echo "function pass: \$k $k"
echo
fail
k=$?
[ $k -gt 0 ] && t || f
echo "function fail: \$k $k"
echo
# direct evaluation of the return value
# note that (...) and $(...) executes in a subshell
# with return value to calling shell
# ((...)) is for math/string evaluation
echo direct evaluations of the return value:
echo ' by if (pass) and if (fail)'
echo $dv
if (pass); then
echo pass has no errors
else
echo pass has errors
fi
if (fail); then
echo fail has no errors
else
echo fail has errors
fi
# this code results in error because of returned string (stdout)
# but comment out the echo statements in pass/fail functions and this code succeeds
echo
echo ' by if $(pass) and if $(fail) ..this succeeds if no echo to stdout from function'
echo $dv
if $(pass); then
echo pass has no errors
else
echo pass has errors
fi
if $(fail); then
echo fail has no errors
else
echo fail has errors
fi
echo
echo ' by if ((pass)) and if ((fail)) ..this always fails'
echo $dv
if ((pass)); then
echo pass has no errors
else
echo pass has errors
fi
if ((fail)); then
echo fail has no errors
else
echo fail has errors
fi
echo
s=$(pass)
r=$?
echo pass, "s: $s , r: $r"
s=$(fail)
r=$?
echo fail, "s: $s , r: $r"