bash 在bash脚本中，如何在while循环条件下调用函数
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In bash script, how to call function in while loop condition
提问by Krishna M
Below is my shell script. How to compare the exit status of function in while loop condition block ? Whatever I return from check1function my code enters into while loop
下面是我的shell脚本。如何比较while循环条件块中函数的退出状态？无论我从check1函数返回什么，我的代码都会进入 while 循环
#!/bin/sh
check1()
{
return 1
}
while [ check1 ]
do
echo $?
check1
if [ $? -eq 0 ]; then
echo "Called"
else
echo "DD"
fi
sleep 5
done
回答by cdarke
Remove the testcommand - also known as [. So:
删除test命令 - 也称为[. 所以：
while check1
do
# Loop while check1 is successful (returns 0)
if check1
then
echo 'check1 was successful'
fi
done
Shells derived from the Bourne and POSIX shells execute a commandafter a conditional statement. One way to look at it is that whileand iftest for success or failure, rather than true or false (although trueis considered successful).
从 Bourne 和 POSIX shell 派生的 shell在条件语句之后执行命令。看它的方法之一是while和if测试成功或失败，而不是真的还是假的（虽然true被认为是成功的）。
By the way, if you must test $?explicitly (which is not often required) then (in Bash) the (( ))construct is usually easier to read, as in:
顺便说一句，如果您必须$?显式测试（这通常不是必需的），那么（在 Bash 中）该(( ))构造通常更易于阅读，如下所示：
if (( $? == 0 ))
then
echo 'worked'
fi
回答by Fernando
The value returned by a function (or command) execution is stored in $?, one solution would be:
函数（或命令）执行返回的值存储在 $? 中，一种解决方案是：
check1
while [ $? -eq 1 ]
do
# ...
check1
done
A nicer and simpler solution may be:
一个更好更简单的解决方案可能是：
while ! check1
do
# ...
done
In this form zero is true and non-zero is false, for example:
在这种形式中，零为真，非零为假，例如：
# the command true always exits with value 0
# the next loop is infinite
while true
do
# ...
You can use !to negate the value:
您可以使用!否定该值：
# the body of the next if is never executed
if ! true
then
# ...
