bfs(1) bfs(1)
NAME
bfs - big file scanner
SYNOPSIS
bfs [-] filename
DESCRIPTION
bfs is a read-only editor that can process much larger files
than standard editors. Files may be up to 1024K bytes (the
maximum possible size) and 32K lines, with up to 512
characters, including newline, per line (255 for 16-bit
machines). bfs is usually more efficient than ed(1) for
scanning a file, since the file is not copied to a buffer.
It is most useful for identifying sections of a large file
where csplit(1) may be used to divide it into more
manageable pieces for editing.
Normally, the size of the file being scanned is printed, as
is the size of any file written with the w command. The
optional - suppresses printing of sizes. Input is prompted
with * if p RETURN are typed as in ed. Prompting can be
turned off again by entering another p RETURN. Note that
messages are given in response to errors if prompting is
turned on.
All address expressions described under ed(1) 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. There is a slight difference in mark names: only
the letters a through z may be used, and all 26 marks are
remembered.
The e, g, v, k, p, q, w, =, ! and null commands operate as
described under ed(1). Commands such as ---, +++-, +++=,
-12, and +4p are accepted. Note that 1,10p and 1,10 will
both print the first ten lines. The f command only prints
the name of the file being scanned; there is no remembered
filename. The w command is independent of output diversion,
truncation, or crunching (see the xo, xt and xc commands,
below). The following additional commands are available:
xf file
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 xf. The xf commands may be nested
to a depth of 10.
xn List the marks currently in use (marks are set by the
k command).
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bfs(1) bfs(1)
xo [file]
Further output from the p and null commands is
diverted to the named file, which, if necessary, is
created mode 666. If file is missing, output is
diverted to the standard output. Note that each
diversion causes truncation or creation of the file.
: label
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.
(. , . )xb/regular expression/label
A jump (either upward or downward) is made to label if
the command succeeds. It fails under any of the
following conditions:
1. Either address is not between 1 and $.
2. The second address is less than the first.
3. The regular expression does not match at least one
line in the specified range, including the first
and last lines.
On success, . is set to the line matched and a jump is
made to label. This command is the only one that does
not 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:
xb/^/ label
is an unconditional jump.
The 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.
xt number
Output from the p and null commands is truncated to at
most number characters. The initial number is 255.
xv[digit][spaces][value]
The variable name is the specified digit following the
xv. xv5100 or xv5 100 both assign the value 100 to
the variable 5. xv61,100p assigns the value 1,100p to
the variable 6. To reference a variable, put a % in
front of the variable name. For example, using the
above assignments for variables 5 and 6:
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bfs(1) bfs(1)
1,%5p
1,%5
%6
will all print the first 100 lines.
g/%5/p
would search globally for the characters 100 and
print each line containing a match. To escape the
special meaning of %, a \ must precede it.
g/".*\%[cds]/p
could be used to match and list lines containing
printf of characters, decimal integers, or strings.
Another feature of the xv command is that the first
line of output from a UNIX® system command can be
stored into a variable. The only requirement is
that the first character of value be an !. For
example:
.w junk
xv5!cat junk
!rm junk
!echo "%5"
xv6!expr %6 + 1
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
value, precede it with a \.
xv7date
stores the value !date into variable 7.
xbz label
xbn label
These two commands will test the last saved return
code from the execution of a UNIX system command
(!command) or nonzero value, respectively, to the
specified label. The two examples below both search
for the next five lines containing the string size:
xv55
: l
/size/
xv5!expr %5 - 1
!if 0%5 != 0 exit 2
xbn l
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xv45
: l
/size/
xv4!expr %4 - 1
!if 0%4 = 0 exit 2
xbz l
xc [switch]
If switch is 1, output from the p and null commands
is crunched; if switch is 0, it is not. Without an
argument, xc reverses switch. Initially switch is
set for no crunching. Crunched output has strings
of tabs and blanks reduced to one blank and blank
lines suppressed.
EXAMPLE
bfs text
will invoke bfs with the file named text.
FILES
/bin/bfs
SEE ALSO
csplit(1), ed(1), regcmp(3X).
DIAGNOSTICS
? for errors in commands, if prompting is turned off.
Self-explanatory error messages when prompting is on.
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