


      BFS(1)                      (UNIX 5.2)                     BFS(1)



      NAME
           bfs - big file scanner

      SYNTAX
           bfs [ - ] name

      DESCRIPTION
           The Bfs command is (almost) like ed(1) except that it is
           read-only and processes much larger files.  Files can be up
           to 1024K bytes (the maximum possible size) and 32K lines,
           with up to 512 characters, including new-line, per line (255
           for 16-bit machines).  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 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 - 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.  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.  There is 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 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 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).




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      BFS(1)                      (UNIX 5.2)                     BFS(1)



                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.  The
                     label is terminated by new-line, and blanks
                     between the : and the start of the label are
                     ignored.  This command may 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, 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.

                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



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      BFS(1)                      (UNIX 5.2)                     BFS(1)



                     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 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

                     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 UNIX system command
                     (!command) or nonzero value, respectively, to the
                     specified label.  The two examples below both
                     search for the next five lines containing the
                     string size.

                          xv55



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      BFS(1)                      (UNIX 5.2)                     BFS(1)



                          : 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.

      SEE ALSO
           csplit(1), ed(1), regcmp(3X).

      DIAGNOSTICS
           ? for errors in commands, if prompting is turned off.
           Self-explanatory error messages when prompting is on.





























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