Syntax
bfs [.] name
Description
bls is like ed (C) except that it is read-only and processes much larger files. Files can be up to 1024K bytes and 32K lines, with up to 255 characters per line. bls is usually more efficient than ed for scanning a file, since the file is not copied to a buffer. It is most useful for iden-tifying sections of a large file where csplit(C) 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 dash (.) suppresses printing of sizes. Input is prompted for with an asterisk (*) when "P" and RETURN are typed. The "P" acts as a toggle, so prompting can be turned off again by entering another "P" and a RETURN. Note that messages are given in response to errors only if prompting is turned on.
All address expressions described under ed are supported. In addition, regular expressions may be surrounded with two symbols other than the standard slash (I) and (?): A greater-than sign (» indicates down-ward search without wraparound, and a less-than sign
«)
indicates upward search without wraparound. Note that parentheses and curly braces are special and need to be escaped with a backslash (\). Since bls uses a different regular expression-matching routine from ed, the regular expressions accepted are slightly wider in scope (see regex (S)). Differences between ed and bls are listed below:+ A regular expression followed by + means one or more times.
For examJ>le, [0·9]+ is equivalent to [0·9][0·9]*.
\{m\} \{m,\} \{m,u\}
Integer values enclosed in \{ \} indicate the number of times the preceding regular expression is to be applied. m is the minimum number and u is a number, less than 256, which is the maximum. If only m is present (e.g., \(m\)), it indicates the exact number of times the regular expression is to be applied. \(m,\} is analogous to \(m,infinity\}. The plus (+) and star (*) operations are equivalent to \(1,\} and \(O,\}
respectively.
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BFS (C) BFS(C) ( ••• )$n The value of the enclosed regular expression is to be returned. The value will be stored in the (n+l)th argument following the subject argument. At most ten enclosed regular expressions are allowed. regex makes its assignments uncon-ditionally.
( ... ) Parentheses are used for grouping. An operator, e.g. *, +,
\{ \}, can work on a single character or a regular expression enclosed in parenthesis. For example, \(a*\(cb+\)*\)$O.
There is also 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 filename. The w command is independent of output diversion, trunca-tion, or crunching (see the xo, xt and xc commands, below). The fol-lowing additional commands are available:
xCfile
( • , • )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 condi-tions:
1. Either address is not between 1 and $.
2. The second address is less than the first.
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BFS (C) BFS(C) 3. The regular expression doesn't match at least one line
in the specified range, including the first and last lines.
On success, dot (.) is set to the line matched and a jump is made to label. This command is the only one that doesn't 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 xbrl label
is an unconditional jump.
The xb command is allowed only if it is read from somewhere 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 a max-imum of 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 refer-ence 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
prints 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. For example,
gI". *\%[cds]/p
could be used to match and list lines containing printf charac-ters, decimal integers, or strings.
Another feature of the xv command is that the first line of output from a Altos UNIX System V command can be stored into a variable.
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BFS (C) BFS(C)
The only requirement is that the first character of value be a !.
For example, xv5!cat junk
!rmjunk
!echo "%5"
xV6!expr %6 + 1
puts the current line in 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 \. For example,
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 an Altos UNIX System V command (!command) or nonzero value, respectively, and jump to the specified label.
The two examples below search for the next five lines contain-ing the strcontain-ing size:
xc [switch]
xv55 : I /size/
xv5!expr %5 -1
!if 0%5 != 0 exit 2 xbn I
xv45 : I /size/
xv4!expr %4 -1
!if 0%4 = 0 exit 2 xbz I
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(C), ed(C), umask(C)
March 11. 1990
BFS-4
BFS(C)
Diagnostics
BFS(C)
? for errors in commands if prompting is turned off. Self-explanatory error messages when prompting is on.
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CAL (C) CAL (C)