Shell - grep stderr output

scnzzh@ZUBT:~$ ansible -i zzh-inventory all --list-hosts | grep WARNING | wc -l
[WARNING]:  * Failed to parse /home/scnzzh/zzh-inventory with yaml plugin: Syntax Error while loading YAML.   did not find expected <document start>  The error
appears to be in '/home/scnzzh/zzh-inventory': line 2, column 1, but may be elsewhere in the file depending on the exact syntax problem.  The offending line appears
to be:  [zservers] zubt ^ here
[WARNING]:  * Failed to parse /home/scnzzh/zzh-inventory with ini plugin: host range must have begin <= end
[WARNING]: Unable to parse /home/scnzzh/zzh-inventory as an inventory source
[WARNING]: No inventory was parsed, only implicit localhost is available
[WARNING]: provided hosts list is empty, only localhost is available. Note that the implicit localhost does not match 'all'
0
scnzzh@ZUBT:~$ ansible -i zzh-inventory all --list-hosts 2>&1 | grep WARNING | wc -l
5