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NAMEbfs — big file scanner DESCRIPTIONbfs
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. - : 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. - (.,.)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.
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
command). - 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:
all print the first 100 lines.
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:
.w junk
xv5!cat junk
!rm junk
!echo "%5"
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. - xbz label
- 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 string
size. First example:
xv55
: l
/size/
xv5!expr %5 - 1
!if [ %5 != 0 ] ; then exit 2 ; fi
xbn l Second Example:
xv45
: l
/size/
xv4!expr %4 - 1
!if [ %4 = 0 ] ; then exit 2 ; fi
xbz l - 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 suppressed.
EXTERNAL INFLUENCESEnvironment VariablesLC_COLLATE
determines the collating sequence used in evaluating regular expressions. LC_CTYPE
determines the classification of characters as letters, and the
characters matched by character class expressions in regular expressions. 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 SupportSingle-byte character code sets are supported. DIAGNOSTICS?
for errors in commands, if prompting is turned off.
Self-explanatory error messages when prompting is on.
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