Bash 等待进程启动
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Bash wait for process start
提问by inukaze
I'm trying to say to Bash , wait for a Process Start / Begin. I'm trying by this way for example:
我试图对 Bash 说，等待进程开始/开始。例如，我正在尝试通过这种方式：
notepad=`pidof notepad.exe`
until [ $notepad > 0 ]
do
taskset -p 03 $notepad
renice -n 5 -p $notepad
sleep 5
renice -n 0 -p $notepad
done
well i have the follow questions:
我有以下问题：
why this generate a file called “0″ (the file are empty) i dont wanna make a new file , just wait for the PID to check execution.
This is a Loop , but if the 2 commands are execute correclty , 1 time how i can continue to done ???
For this its better use "until or while" ???
Another ideas for wait Process Start or Begin ???
为什么这会生成一个名为“0”的文件（文件为空）我不想创建一个新文件，只需等待 PID 检查执行。
这是一个循环，但如果这 2 个命令正确执行，我如何继续执行 1 次？？？
为此，它更好地使用“直到或同时”？？？
等待进程开始或开始的另一个想法？？？
回答by that other guy
There are multiple issues with your code:
您的代码存在多个问题：
- pidof doesn't print 0 or -1 if there's no process, so your logic is wrong
- pidof can return multiple pids if there are multiple processes, which would break your comparison
>has to be escaped in[ ]otherwise your code is equivalent to[ $notepad ] > 0, directing to a file.>isn't even the right operator. You wanted-gt, but as mentioned in point #1 and #2, you shouldn't compare numbers.untilruns the loop until the condition is true. it doesn't wait for the condition to become true, and then run the loop.
- 如果没有进程，pidof 不会打印 0 或 -1，所以你的逻辑是错误的
- 如果有多个进程，pidof 可以返回多个 pid，这会破坏您的比较
>必须转义，[ ]否则您的代码等效于[ $notepad ] > 0, 指向文件。>甚至不是正确的操作员。您想要-gt，但如第 1 点和第 2 点所述，您不应该比较数字。until运行循环直到条件为真。它不会等待条件变为真，然后运行循环。
This is how you should do it:
你应该这样做：
# Wait for notepad to start
until pids=$(pidof notepad)
do
sleep 1
done
# Notepad has now started.
# There could be multiple notepad processes, so loop over the pids
for pid in $pids
do
taskset -p 03 $pid
renice -n 5 -p $pid
sleep 5
renice -n 0 -p $pid
done
# The notepad process(es) have now been handled
回答by dwanderson
To answer your first question: '>' is not the mathematical/comparison operator 'greater than'; it's bash's way of letting you pipe output to a file (handle).
回答你的第一个问题：“>”不是数学/比较运算符“大于”；这是 bash 让您将输出通过管道传输到文件（句柄）的方式。
echo "some text" > myfile.txt
will create a file named myfile.txt, and '>' sent the output of the command into that file. I would imagine that your file '0' has the pid in it, and nothing else.
将创建一个名为 myfile.txt 的文件，并且 '>' 将命令的输出发送到该文件中。我想你的文件 '0' 里面有 pid，没有别的。
Instead, try -gt(or related variants: -ge, -lt, -le, -eg, -ne) to test if one value is greater than (or: greater than or equal, less than, less than or equal, equal, not equal, respectively) to see if that helps. That is,
相反，尝试-gt（或相关变体：-ge, -lt, -le, -eg, -ne）测试一个值是否大于（或：分别大于或等于、小于、小于或等于、等于、不等于）以查看是否有帮助。那是，
until [ $notepad -gt 0 ]
回答by damienfrancois
If I understand correctly, you want to wait until notepad is launched. Then the pidof must be inside your loop.
如果我理解正确，您要等到记事本启动。然后 pidof 必须在您的循环内。
while ! pidof notepad.exe >> /dev/null ;
do
sleep 1
done
notepad=$(pidof notepad.exe)
taskset -p 03 $notepad
renice -n 5 -p $notepad
sleep 5
renice -n 0 -p $notepad
