bfs(1)

Synopsis

Description

bfs processes supplementary code set characters in file, and recognizes supplementary code set characters in the labels given to the :, xb, xbn, and xbz commands (see below) according to the locale specified in the LC_CTYPE environment variable (see LANG on environ(5)). In regular expressions, pattern searches are performed on characters, not bytes (see ed(1)).

Normally, the size in bytes 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 <Return> are typed, as in ed. Prompting can be turned off again by inputting another ``P'' and <Return>. 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.

The e, g, v, k, p, q, =, ! 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. 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 with mode 666 (readable and writable by everyone), unless your umask setting dictates otherwise; see umask(1). 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. The label is terminated by new-line, and blanks between the : and the label are ignored. This command may also be used to insert comments into a command file, since labels need not be referenced. label may contain supplementary code set characters.

( .,. )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, 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 possible. label may contain supplementary code set characters.

xt number

Output from the p and null commands is truncated to at most number displayed columns. 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

all print 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.

   g/".*\%[cds]/p

could be used to match and list lines containing a printf 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 ``!''. For example:

   .w junk
   xv5!cat junk
   !rm junk
   !echo "%5"
   xv6!expr %6 + 1

puts the current line into 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 ``\''.

   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 a UNIX system command (!command) for zero or nonzero value, respectively, and jump to the specified label. label may contain supplementary code set characters. The two examples below both search for the next five lines containing the string size.

   xv55
   : l
   /size/
   xv5!expr %5 - 1
   !test 0 = %5
   xbn l
   

   xv45
   : l
   /size/
   xv4!expr %4 - 1
   !test 0 != %4
   xbz l

xc [switch]

If switch is 1, output from the p and null commands is crunched; if switch is 0 it is not. 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

References