Col

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Linux命令：col

功能说明：过滤控制字符。

语　　法：col [-bfx][-l<缓冲区列数>]

补充说明：在许多UNIX说明文件里，都有RLF控制字符。当我们运用shell特殊字符">"和">>"，把说明文件的内容输出成纯文本文件时，控制字符会变成乱码，col指令则能有效滤除这些控制字符。

参　　数：
 -b   过滤掉所有的控制字符，包括RLF和HRLF。
 -f   滤除RLF字符，但允许将HRLF字符呈现出来。
 -x   以多个空格字符来表示跳格字符。
 -l<缓冲区列数>   预设的内存缓冲区有128列，您可以自行指定缓冲区的大小。 

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英文版本，欢迎翻译：

NAME col - filter reverse line feeds from input

SYNOPSIS col [-bfpx] [-l num]

DESCRIPTION Col filters out reverse (and half reverse) line feeds so the output is in the correct order with only forward and half forward line feeds, and re? places white-space characters with tabs where possible. This can be use? ful in processing the output of nroff(1) and tbl(1).

Col reads from standard input and writes to 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.

-lnum 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 alternate 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 dis? play a warning message.

SEE ALSO expand(1), nroff(1), tbl(1)

STANDARDS The col utility conforms to the Single UNIX Specification, Version 2. The -l option is an extension to the standard.

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