changing col(1) command stdout as fully buffered?

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06-09-2006

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changing col(1) command stdout as fully buffered?

Hi All,

I am talking about unix col(1) command used for some reverse line filtering etc.
And I notice that the stdout of this command is line buffered i.e. the stdout will flush the data in its buffer line by line. So the number of writes performed by stdout are more.

So now if I make stdout as fully buffered it will reduce the write hits.

But if I do these changes I think there will some problems
-> when slow terminals use col(1) as command , then the turn around time will get reduce for it self.
eg: cat file | col -b | lp
Here lp will receive data in terms of buffer size but before it was receving in terms of each lines.

So can I change change col(1) command's stdout to fully buffered?

So do any of you know some more problems related with this change , and can I see some link about col(1) command design stating that it should be either line buffered or fully buffered etc.

Waiting for positive replay,
Sunil kumar.

sunilsbjoshi

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LEARN ABOUT NETBSD

col

COL(1)							    BSD General Commands Manual 						    COL(1)

NAME

     col -- filter reverse line feeds from input

SYNOPSIS

     col [-bfpx] [-l num]

DESCRIPTION

     col filters out reverse (and half reverse) line feeds so that the output is in the correct order with only forward and half forward line
     feeds, and replaces white-space characters with tabs where possible.  This can be useful in processing the output of nroff(1) and tbl(1).

     col reads from the standard input and writes to the standard output.

     The options are as follows:

     -b        Do not output any backspaces, printing only the last character written to each column position.

     -f        Forward half line feeds are permitted (``fine'' mode).  Normally characters printed on a half line boundary are printed on the fol-
	       lowing line.

     -p        Force unknown control sequences to be passed through unchanged.	Normally, col will filter out any control sequences from the input
	       other than those recognized and interpreted by itself, which are listed below.

     -x        Output multiple spaces instead of tabs.

     -l num    Buffer at least num lines in memory.  By default, 128 lines are buffered.

     The control sequences for carriage motion that col understands and their decimal values are listed in the following table:

     ESC-7	      reverse line feed (escape then 7)
     ESC-8	      half reverse line feed (escape then 8)
     ESC-9	      half forward line feed (escape then 9)
     backspace	      moves back one column (8); ignored in the first column
     carriage return  (13)
     newline	      forward line feed (10); also does carriage return
     shift in	      shift to normal character set (15)
     shift out	      shift to alternative character set (14)
     space	      moves forward one column (32)
     tab	      moves forward to next tab stop (9)
     vertical tab     reverse line feed (11)

     All unrecognized control characters and escape sequences are discarded.

     col keeps track of the character set as characters are read and makes sure the character set is correct when they are output.

     If the input attempts to back up to the last flushed line, col will display a warning message.

SEE ALSO

     expand(1), nroff(1), tbl(1)

STANDARDS

     The col utility conforms to X/Open Portability Guide Issue 4, Version 2 (``XPG4.2'').  The -l option is an extension to the standard.

HISTORY

     A col command appeared in Version 6 AT&T UNIX.

BSD
								 February 22, 1999							       BSD