Linux filter control character command col
The function of the col command is to filter control characters. It is also a member of the pipeline command family.
In many UNIX description files, there are RLF control characters. When we use the shell special characters ">" and ">>" to output the contents of the description file to a plain text file, the control characters will become garbled characters. The col command can effectively filter out these control characters.
-x converts the tab key into a space key equivalent
-b When there is a backslash (/) in the text, only the character following the backslash is retained
-f filters out RLF characters but allows HRLF characters to be rendered.
-l <buffer columns> The default memory buffer has 128 columns, and you can specify the buffer size yourself.
As for the usage examples of this command, I will use two examples provided by Bird Brother to illustrate.
Example 1: Use cat -A to display all special keys, and then use col to convert [tab] to blank.
[root@www ~]# cat -A /etc/man.config <== At this time you will see a lot of ^I symbols, that is tab
[root@www ~]# cat /etc/man.config | col -x | cat -A | more
# Hey! In this way, the [tab] key will be replaced by the space bar, and the output will be much more beautiful!
Example 2: Convert the man page of col to a plain text file in /root/col.man
[root@www ~]# man col > /root/col.man
[root@www ~]# vi /root/col.man
COL(1) BSD General Commands Manual COL(1)
N^HNA^HAM^HME^HE
c^Hco^Hol^Hl - filter reverse line feeds from input
S^HSY^HYN^HNO^HOP^HPS^HSI^HIS^HS
c^Hco^Hol^Hl [-^Hb^Hbf^Hfp^Hpx^Hx] [-^Hl^Hl _^Hn_^Hu_^Hm]
# You read it right! Some special buttons in the man page are used as special keys and color displays,
# so this file will have a bunch of weird characters (with ^) as shown above
[root@www ~]# man col | col -b > /root/col.man
col is often used to save man pages as plain text files for easy reference! For detailed usage of other options, use man col.
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