NAME

fb - search blocks of lines for text patterns


SYNOPSIS


fb
[-acx] [-ln] [-sexpr [-sexpr]] expr [expr ...]


DESCRIPTION

"Fb"
(find block) searches blocks or groups of lines in a file for
text patterns.
It is similar to 'find' except that if a pattern is found,
the entire block of lines is copied to standard output,
rather than simply the line in which the pattern occurred.
Thus it is useful for searching mailing lists, bibliographies,
and similar files where several lines are grouped together to
form cohesive units.

The search patterns may be any regular expression as described
in the 'ed' and 'find' writeups.

"Fb"
assumes the blocks of lines are separated by an empty line or a
line containing only blanks.
When "fb" is called without any options, standard input is read
and each line is checked to see if it matches any of the regular
expressions given as arguments.
If any matches are found,
the entire block is printed on standard output.

Other options include:



-a      Only print the block if ALL the arguments are found within it


-x      Only print the block if none of the arguments are
found within it


-c      Only print a COUNT of the number of blocks found which
match/don't match the expressions


-sexpr  Use 'expr' as the block separator (instead of a blank or
empty line).  "Expr" can be a regular expression just as
the search arguments can.

If two "-sexpr" arguments are given, the first one is considered
to be the pattern which starts a block (e.g. -ssubroutine) and
the second is considered the pattern which ends a block
(e.g. -send).


-ln     prints only the first 'n' lines of the block;
if the block contains less than 'n' lines, the block is padded
out with blank lines.



Care should be taken when using the characters % $ [ ] ! * @ and
any shell characters
in the text pattern. It is often necessary to enclose the
entire substitution pattern in quotes.


FILES

A scratch file ("fbt") is used if the internal line buffer
becomes full.


SEE ALSO

find, ed

For a complete description of regular expressions, see
"Software Tools" pages 135-154.


DIAGNOSTICS

Error messages are given if:


a)  One of the patterns given is illegal

b)  Too many separators are given (2 are allowed)

c)  The maximum number of expressions is exceeded (9 are allowed)

d)  There are problems opening the scratch file (when the block line
buffer fills up).


If the following messages show up, something is dreadfully wrong:

a)  "Illegal default separator"

b)  "Block buffer overflow"



AUTHORS

Debbie Scherrer (Lawrence Berkeley Laboratory)


BUGS

An expression may not start with a minus sign (-).

Regular expressions can not span line boundaries.