BFS(1)BFS(1)NAMEbfs - big file scanner
/usr/bin/bfs [-] filename
The bfs command is (almost) like ed(1) 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(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) 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 (write) command. The optional − sup‐
presses printing of sizes. Input is prompted with * if P and a carriage
return are typed, as in ed(1). 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.
All address expressions described under ed(1) are supported. In addi‐
tion, regular expressions may be surrounded with two symbols besides /
indicates downward search without wrap-around, and
indicates upward search without wrap-around.
There is a slight difference in mark names; that is, 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 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:
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.
List the marks currently in use (marks are set by the k command).
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 setting (see umask(1))
dictates otherwise. If file is missing, output is diverted to the
standard output. Note that each diversion causes truncation or
creation of the file.
This positions a label in a command file. The label is terminated
by new-line, and blanks between the : (colon) 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
On success, . (dot) 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
Output from the p and null commands is truncated to, at most, num‐
ber characters. The initial number is 255.
The variable name is the specified digit following the xv. The com‐
mands 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:
will all print the first 100 lines.
would globally search for the characters 100 and print each line
containing a match. To escape the special meaning of %, a \ must
could be used to match and list %c, %d, or %s formats (for example,
"printf"-like statements) 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 !.
xv6!expr %6 + 1
would put the current line into variable 35, print it, and incre‐
ment the variable 36 by one. To escape the special meaning of ! as
the first character of value, precede it with a \.
stores the value !date into variable 7.
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:
xv5!expr %5 − 1
!if 0%5 != 0 exit 2
xv4!expr %4 − 1
!if 0%4 = 0 exit 2
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
The following operand is supported:
Any file up to 1024K bytes and 32K lines, with up to 512
characters, including new-line, per line (255 for 16-bit
machines). filename can be a section of a larger file which
has been divided into more manageable sections for editing
by the use of csplit(1).
The following exit values are returned:
Successful completion without any file or command errors.
An error occurred.
SEE ALSOcsplit(1), ed(1), umask(1), attributes(5)DIAGNOSTICS
Message is ? for errors in commands, if prompting is turned off. Self-
explanatory error messages are displayed when prompting is on.
May 20, 1996 BFS(1)