How do I grep for an exact word as with "grep -w" in Linux?

How do I grep for an exact word as with "grep -w" in Linux? Added: 09/12/03

From 11.11 onwards, the -w option is supported. Otherwise, use:

$ grep -E "(^|[^[:alnum:]_])(<word_to_be_searched>)([^[:alnum:]_]|$)"

or install GNU grep and use its -w option.

[an error occurred while processing this directive]