man grep: read a directory

[Dan Jacobson]

       -d ACTION, --directories=ACTION
              If an input file is a directory, use ACTION to process it.  By 
default, ACTION
              is read, which means that directories are read just as if they  
were  ordinary
              files.   If  ACTION  is  skip, directories are silently skipped.  
If ACTION is


Say if no ACTION is given, the default is to ... and
say if no -d     is given, the default is to ...

Also say what you mean by "read a directory".

# grep -c sys /var/log/
0
# ls /var/log/|grep sys
syslog
syslog.0
syslog.1.gz
syslog.2.gz
syslog.3.gz
syslog.4.gz
syslog.5.gz
syslog.6.gz
sysstat
# grep -d read -c sys /var/log/
0
# cat /var/log/|grep sys
cat: /var/log/: Is a directory