bfs(1) DG/UX R4.11MU05 bfs(1)
NAME
bfs - big file scanner
SYNOPSIS
bfs [ - ] name
DESCRIPTION
The bfs command is like ed(1), but 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 newline. 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 csplit(1) can 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 you type P
and a newline as in ed. Turn prompting off again by inputting
another P and newline. Note that 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. For 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 will both print the first ten
lines. The f command prints only 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. If file
is missing, output is diverted to the standard output. Note
that each diversion truncates or creates 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 also inserts 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 if: Either address is not between 1
and $.
The second address is less than the first, or
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. If the command fails, the jump is not made and the next
statement is executed. This command is the only one that does
not issue an error message on bad addresses, so you can use it
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
will all print the first 100 lines.
g/%5/p
would globally search 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 DG/UX system command can be stored into a
variable. The only requirement is that the first character of
value be !. 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 \.
xv7\!date
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 DG/UX system command (!command) or nonzero value,
respectively, to the specified label. The two examples below
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/
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.
DIAGNOSTICS
? for errors in commands, if prompting is turned off.
Self-explanatory error messages when prompting is on.
SEE ALSO
csplit(1), ed(1).
regcmp(3X)
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