mailbox.log file type

[bartounet]

hello this morning i want to do a "grep" on my mailbox.log and i have this message...

zimbra@zimbraprod:~/log> cat mailbox.log | grep antony
Binary file (standard input) matches

so i have investigate and i have understand...

my mailbox.logs are in "data" file type !!!

mailbox.log:            data
mailbox.log.2010-08-24: ASCII C++ program text, with very long lines
mailbox.log.2010-08-25: ASCII text, with very long lines
mailbox.log.2010-08-26: ASCII C++ program text, with very long lines
mailbox.log.2010-08-27: ASCII C++ program text, with very long lines
mailbox.log.2010-08-28: ASCII text
mailbox.log.2010-08-29: ASCII text, with very long lines
mailbox.log.2010-08-30: ASCII text
mailbox.log.2010-08-31: ASCII C++ program text, with very long lines
mailbox.log.2010-09-01: ASCII C++ program text, with very long lines
mailbox.log.2010-09-02: ASCII C++ program text, with very long lines
mailbox.log.2010-09-03: ASCII C++ program text, with very long lines
mailbox.log.2010-09-04: ASCII C++ program text, with very long lines
mailbox.log.2010-09-05: ASCII text
mailbox.log.2010-09-06: ASCII text, with very long lines
mailbox.log.2010-09-07: ASCII English text, with very long lines
mailbox.log.2010-09-08: ASCII C++ program text, with very long lines
mailbox.log.2010-09-09: data
mailbox.log.2010-09-10: data
mailbox.log.2010-09-11: data
mailbox.log.2010-09-12: data
mailbox.log.2010-09-13: data
mailbox.log.2010-09-14: data
mailbox.log.2010-09-15: data

i don't understand when unix decide to do an ASCII file or a data file ...

[Klug]

Just to add a piece of information : this happens on a SLES11 64bits server.