bfs(1) (Directory and File Management Utilities) bfs(1)
NAME
bfs - big file scanner
SYNOPSIS
bfs [ - ] file
DESCRIPTION
The bfs command is similar to ed except that it is read-only and
processes much larger files. Files can be up to 1024K bytes and 32K
lines, with up to 512 characters, including new-line, per line (255
for 16-bit machines). bfs is usually more efficient than ed 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 the csplit
command can 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 and a
carriage return are typed, as in ed. Prompting can be turned off
again by inputting another P and carriage return. Messages are given
in response to errors if prompting is turned on.
All address expressions described under 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. 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. Commands such as ---, +++-, +++=, -12, and +4p are
accepted. Note that 1,10p and 1,10 both print the first ten lines.
The f command only prints the name of the file being scanned; there
is no remembered file name. 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).
xo [file]
Further output from the p and null commands is diverted to
the named file, which, if necessary, is created mode 666
(readable and writable by everyone), unless your umask
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bfs(1) (Directory and File Management Utilities) bfs(1)
setting dictates otherwise; see umask(1). 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 new-line, 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.
The commands xv5100 or xv5 100 both assign the value 100
to the variable 5. The command 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:
1,%5p
1,%5
%6
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bfs(1) (Directory and File Management Utilities) bfs(1)
all print the first 100 lines.
g/%5/p
globally searches for the characters 100 and prints 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 a 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
puts the current line into variable 5, prints it, and
increments the variable 6 by one. To escape the special
meaning of ! as the first character of value, precede it
with a \.
xv7\!date
stores the value !date into variable 7.
xbz label
xbn label
These two commands 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
xv45
: l
/size/
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bfs(1) (Directory and File Management Utilities) bfs(1)
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.
SEE ALSO
csplit(1), ed(1), umask(1).
DIAGNOSTICS
? for errors in commands, if prompting is turned off. Self-
explanatory error messages when prompting is on.
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