Java进程执行“ tail -f test.log | grep abc”无法获得任何输出

Question

I've written a java program to execute linux command. But I find it can not get any output from the command "tail -f test.log | grep abc"

Below are several examples:

"tail -n 100 test.log | grep abc" -- works
"tail -f test.log" -- works  
"tail -f test.log | grep abc" -- not works

My Java code

String[] cmd = new String[] {"/bin/sh", "-c", "tail -f /Users/Alexis/Test/test.log | grep abc"};
InputStream inputStream = Runtime.getRuntime().exec(cmd).getInputStream();
byte[] bb = new byte[8];
int i = 0;
while ((i = inputStream.read(bb)) != -1) {
    System.out.println("received : " + new String(bb, Charsets.UTF_8));
}

When I echo something into test.log, I can't get any output.

Answer 1

finally I use 'tail -f test.log | unbuffer -p grep abc' and it works

Also, you can use 'tail -f test.log | stdbuf -o0 grep abc'