Piping To Grep Is Giving Too Many Results

I’m trying to check whether a particular service is running via a Linux terminal, and the following command doesn’t seem to be filtering the results as expected. Not sure what I’m doing wrong…

service --status-all | grep subversion

This produces several lines of output, including, for example,

 [ ? ] Networking

I’m not sure why this is happening, since the string “subversion” is not contained within the above line…

Answer

You should use:

service --status-all |& grep subversion

Because the services without a status ([ ? ]) are sent to stderr, which is not pipelined to grep (and then it is printed on your terminal regardless).

|& sends stderr to stdout so grep is able to filter it.