docker ps -f should return nonzero exit status for no matches

[damobrisbane]

Description

As per vdemeester comment, re-opening moby/moby#35057.

Reason to close was command will return zero even when "docker ps" returns no containers.

If instead docker ps returns ie 1 or not zero when container is not running, it then enables better integration with other tooling:

# Conventional Exit Code Use - ls command on folder exists, not-exists
 
if [[ $( ls /tmp 2>/dev/null ) ]]; then echo "folder exists"; else echo "folder does not exist"; fi

folder exists
 
if [[ $( ls /tmpXX 2>/dev/null ) ]]; then echo "folder exists"; else echo "folder does not exist"; fi

folder does not exist

# Docker ps - Less Useful Zero Exit Code

if [[ $( docker ps --filter label=runningimage=no 2>/dev/null ) ]]; then echo "container is running"; else echo "container is not running"; fi

container is running

??? WHY
 
eg, docker ps - no containers are running
CONTAINER ID   IMAGE     COMMAND   CREATED   STATUS    PORTS     NAMES
.... 

Another closer example, "pgrep" - listing processes by process matching, clearly explains rationale:

...
       -c, --count
              Suppress  normal  output;  instead print a count of matching processes.  When count does not match anything, e.g. returns zero, the command will return
              non-zero value. Note that for pkill and pidwait, the count is the number of matching processes, not the processes that were  successfully  signaled  or
              waited for.