PWB1/usr/man/man1/bfs.1

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.tr ~.
.th BFS I 5/31/77
.if t .ds q \(aa
.if n .ds q '
.sh NAME
bfs \*- big file scanner
.sh SYNOPSIS
.bd bfs
[
.bd \*-
] name
.sh DESCRIPTION
.it Bfs
is (almost) like
.it ed\^\c
(I)
except that it is read-only
and processes much bigger files.
Files can be up 1024K bytes (the maximum possible size) and
32K lines, with up to 255 characters per line.
.it Bfs
is usually more efficient than
.it ed
for scanning a file,
since the file is not copied to a buffer.
.s3
Normally,
the size of the file being scanned is printed,
as is the size of any file written with the
.it w
command.
The optional
.bd \*-
suppresses printing of sizes.
Input is prompted with `*' if
`P' and a carriage return is typed as in
.it ed.
Prompting can be turned off again by
inputting another `P' and carriage
return.
Note that messages are given in response
to errors if prompting is turned on.
.s3
All address expressions described under
.it ed
are supported.
In addition, regular expressions may be surrounded with two
symbols besides `/' and `?': `>' indicates
downward search without wrap-around,
and `<' indicates upward search without wrap-around.
Since
.it bfs
uses a different regular expression-matching routine
from 
.it ed,
the regular expressions accepted are slightly wider in scope (see
.it regex\^\c
(III)).
There is a slight difference in mark names: only the letters
`a' through `z' may be used,
and all 26 marks are remembered.
.s3
The
.it e,
.it g,
.it v,
.it k,
.it n,
.it p,
.it q,
.it w,
.it =,
.it !
and null
commands operate
as described under
.it ed.
Commands such as `\*-\*-\*-', `+++\*-',
`+++=', `\*-12', and `+4p' are accepted.
Note that `1,10p' and `1,10' will both print 
the first ten lines.
The
.it f
command only prints the name of the file being scanned;
there is no 
.it remembered
file name.
The
.it w
command is independent of output diversion,
truncation or crunching
(see the
.it xo,
.it xt
and
.it xc
commands, below).
The following additional commands are available:
.s3
.lp +10 5
xf file
.br
Further commands are taken from the named file.
When an end-of-file is reached,
an interrupt signal is received or an error occurs,
reading resumes with the
file containing the
.it xf.
.it Xf
commands may be nested to a depth of 10.
.s3
.lp +10 5
xo [file]
.br
Further output from the
.it p
and null
commands is diverted to the named file,
which, if necessary, is created mode 666.
Plain `xo' diverts output back to the standard output.
Note that each diversion causes truncation
or creation of the file.
.s3
.lp +10 5
: label
.br
This positions a label in a command file.
The label is terminated by newline, and
blanks between the `:' and the start of the label are ignored.
This command may also be used to insert comments
into a command file,
since labels need not be referenced.
.s3
.lp +10 5
( \fB. \fR, \fB. \fR)\|xb/regular expression/label
.br
A jump (either upward or downward) is made to the named label if
the command succeeds.
It fails under any of the following conditions:
.s3
.lp +16 3
.ne 5
1. Either address is not between 1 and $.
.lp +16 3
2. The second address is less than the first.
.lp +16 3
3. The regular expression doesn't match at least one line
in the specified range, including the first and last lines.
.lp +10 0
.s3
On success, `.' is set to the line matched and a jump
is made to the label.
This command is the only one that doesn't issue an error
message on bad addresses, so it may be used to
test whether addresses are bad before other commands are executed.
Note that the command
.s3
.lp +16 0
xb/^/ label
.lp +10 0
.s3
is an unconditional jump.
.s3
The
.it xb
command is allowed only if
it is read from someplace other than a terminal.
If it is read from a pipe only a downward jump is possible.
.lp +10 0
.s3
.lp +10 5
xt number
.br
Output from the
.it p
and null commands is
truncated to at most
.it number
characters.
The initial number is 255.
.s3
.lp +10 5
xv[digit: 0\*-9][optional spaces][value]
.br
The variable name is the specified
.it digit
following the `xv'. `xv5100' or `xv5 100' both
assign the
.it value 
`100' to the
.it variable
`5'. `xv61,100p' assigns the
.it value
`1,100p' to 
.it variable
`6'. To reference the variable put a `%'
in front of the variable name.
For example, using the above assignments
for the variables `5' and`6':
.s3
.lp +16 0
1,%5p
.lp +16 0
1,%5
.lp +16 0
%6
.lp +10 0
.s3
will all print the first 100 lines.
.s3
.lp +16 0
g/%5/p
.lp +10 0
.s3
would globally search for the characters `100'
and print each line containing a match.
To escape the special meaning of `%', a `\\' must
precede it.
.s3
.lp +16 0
g/".*\\%[cds]/p
.lp +10 0
.s3
could be used to match and list lines 
containing
.it printf
of characters,decimal integers, or strings.
.s3
Another feature of the
.it xv
command is that the first line
of output from a UNIX command can
be stored into a variable. The only
requirement is that the first character
of
.it value
be an `!'. For example:
.s3
.lp +16 0
\fB~\fRw junk
.lp +16 0
xv5!cat junk
.lp +16 0
!rm junk
.lp +16 0
!echo "%5"
.lp +16 0
xv6!expr %6 + 1
.lp +10 0
.s3
would put the current line into variable `5',
print it, and increment the variable `6' by one.
To escape the special meaning of `!' as the
first character of
.it value,
precede it with a `\\'.
.s3
.lp +16 0
xv7\\!date
.lp +10 0
.s3
stores the
value `!date' into
variable `7'.
.s3
.lp +10 5
xbz label
.lp +10 5
xbn label
.br
These two commands will test the last saved
.it return
.it code
from the execution of a unix command
(!UNIX command) and branch on a zero
or nonzero value, respectively, to the
specified label. The two examples below both 
search for the next five lines containing
the string `size'.
.s3
.lp +16 0
xv55
.lp +16 0
: l
.lp +16 0
/size/
.lp +16 0
xv5!expr %5 - 1
.lp +16 0
!if 0%5 != 0 exit 2
.lp +16 0
xbn l
.s3
.lp +16 0
xv45
.lp +16 0
: l
.lp +16 0
/size/
.lp +16 0
xv4!expr %4 - 1
.lp +16 0
!if 0%4 = 0 exit 2
.lp +16 0
xbz l
.s3
.s3
.lp +10 5
xc [switch]
.br
If
.it switch
is 1, output from the
.it p
and null commands is crunched;
if
.it switch
is 0 it isn't.
Plain
`xc'
reverses the switch.
Initially the switch is set for no crunching.
Crunched output has strings of tabs and blanks reduced
to one blank and blank lines suppressed.
.s3
.i0
.ne 5
.fi
.i0
.sh "SEE ALSO"
ed(I), regex(III)
.br
.ne 20
.sh DIAGNOSTICS
`?' for errors in commands, if prompting is turned off.
Self-explanatory error messages when prompting is on.
.tr ~~