bfs - big file scanner
bfs [-] name
bfs is similar to ed except that it is read-only (see ed(1)) bfs can
handle files with up to 32K - 1 lines; each line can contain up to 512
characters, including the new-line character. bfs is usually more
efficient than ed for scanning a file, since the file is not copied to
a buffer. Historically, this command was most useful for identifying
sections of a large file where csplit could be used to divide it into
more manageable pieces for editing (see csplit(1)). However, most
editors now support files larger than the above-mentioned limits.
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 pressing Return. Note that messages
are given in response to errors if prompting is turned on.
bfs supports the Basic Regular Expression (RE) syntax (see regexp(5))
with the addition that a null RE (e.g., //) is equivalent to the last
RE encountered. All address expressions described under ed are
supported. In addition, regular expressions can 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 can
be used, and all 26 marks are remembered.
The e, g, v, k, n, 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. Xf commands may be nested to a
depth of 10.
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.
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: label This positions a label in a command file. label is
terminated by a new-line, and blanks between the : and
the start of label are ignored. This command can also
be used to insert comments into a command file, since
labels need not be referenced.
A jump (either upward or downward) is made to label if
the command succeeds. It fails under any of the
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. Thus it
can be used to test whether addresses are bad before
other commands are executed. Note that the command
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.
xn List the marks currently in use (marks are set by the k
xt number Output from the p and null commands is truncated to at
most number characters. The initial number is 255.
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:
all print the first 100 lines.
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globally searches for the characters 100 and prints
each line containing a match. To escape the special
meaning of %, a \ must precede it. For example, to
match and list lines in a program file that contain
printf() format strings specifying characters, decimal
integers, or strings, the following could be used:
Another feature of the xv command is that the first
line of output from an HP-UX command can be stored into
a variable. The only requirement is that the first
character of value be an !. For example:
xv6!expr %6 + 1
each 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 \.
stores the value !date into variable 7.
xbn label These two commands test the last saved return code from
the execution of an HP-UX system command (!command) for
a zero or non-zero value, respectively, and cause a
branch to the specified label. The two examples below
both search for the next five lines containing the
xv5!expr %5 - 1
!if [ %5 != 0 ] ; then exit 2 ; fi
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xv4!expr %4 - 1
!if [ %4 = 0 ] ; then exit 2 ; fi
xc [switch] If switch is 1, output from the p and null commands is
crunched; if switch is 0 it isn't. 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
LC_COLLATE determines the collating sequence used in evaluating
LC_CTYPE determines the classification of characters as letters, and
the characters matched by character class expressions in regular
If LC_COLLATE or LC_CTYPE is not specified in the environment or is
set to the empty string, the value of LANG is used as a default for
each unspecified or empty variable. If LANG is not specified or is
set to the empty string, a default of "C" (see lang(5)) is used
instead of LANG. If any internationalization variable contains an
invalid setting, bfs behaves as if all internationalization variables
are set to "C". See environ(5).
International Code Set Support
Single-byte character code sets are supported.
? for errors in commands, if prompting is turned off. Self-
explanatory error messages when prompting is on.
csplit(1), ed(1), lang(5), regexp(5).
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