如何判断某个设备文件是否存在

问：如何在shell里面实现，判断设备文件是否存在，如果不存在则重新判断，直到它存在，如果存在了则往下跑?

假设要判断的设备文件是一个字符设备，例如：/dev/input/event4

while true; do
if [ ! -c /dev/input/event4 ]; then
echo "Can not find /dev/input/event4"
sleep 1
continue
else
echo "Found /dev/input/event$event_num"
do something
break
fi
done

另外，附上shell if 语言常用的参数说明

-a file exists.
-b file exists and is a block special file.
-c file exists and is a character special file.
-d file exists and is a directory.
-e file exists (just the same as -a).
-f file exists and is a regular file.
-g file exists and has its setgid(2) bit set.
-G file exists and has the same group ID as this process.
-k file exists and has its sticky bit set.
-L file exists and is a symbolic link.
-n string length is not zero.
-o Named option is set on.
-O file exists and is owned by the user ID of this process.
-p file exists and is a first in, first out (FIFO) special file or
named pipe.
-r file exists and is readable by the current process.
-s file exists and has a size greater than zero.
-S file exists and is a socket.
-t file descriptor number fildes is open and associated with a
terminal device.
-u file exists and has its setuid(2) bit set.
-w file exists and is writable by the current process.
-x file exists and is executable by the current process.
-z string length is zero.