06-25-2013
The sed command uses a substitute command ( s/.../.../ ) . The first part of the expression contains a basic regular expression (regex). The escaped parentheses \( and \) are used to group parts of matched text that can be back referenced by \1 in the second part of the s-command.
So in this case only the second colon is outside the grouped part and does not get back referenced, so effectively it gets discarded. If we apply this to your input file then the first match is :8:, which gets substituted with :8|. At the end of the expression is the letter g, which is the "global" flag, which means that the operation should be repeated for every occurrence on the line.
So this will be repeated, and crucial here, is that the next match will start after the previous match, so next up will be :4: which becomes :4| and then :14: becomes :14| and so on...
Last edited by Scrutinizer; 06-25-2013 at 01:49 AM..
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LEARN ABOUT CENTOS
catman
CATMAN(8) Manual pager utils CATMAN(8)
NAME
catman - create or update the pre-formatted manual pages
SYNOPSIS
catman [-d?V] [-M path] [-C file] [section] ...
DESCRIPTION
catman is used to create an up to date set of pre-formatted manual pages known as cat pages. Cat pages are generally much faster to dis-
play than the original manual pages, but require extra storage space. The decision to support cat pages is that of the local administra-
tor, who must provide suitable directories to contain them.
The options available to catman are the manual page hierarchies and sections to pre-format. The default hierarchies are those specified as
system hierarchies in the man-db configuration file, and the default sections are either the colon-delimited contents of the environment
variable $MANSECT or the standard set compiled into man if $MANSECT is undefined. Supplying catman with a set of whitespace-delimited sec-
tion names will override both of the above.
catman makes use of the index database cache associated with each hierarchy to determine which files need to be formatted.
OPTIONS
-d, --debug
Print debugging information.
-M path, --manpath=path
Specify an alternate colon-delimited manual page hierarchy search path. By default, this is all paths indicated as system hierar-
chies in the man-db configuration file.
-C file, --config-file=file
Use this user configuration file rather than the default of ~/.manpath.
-?, --help
Print a help message and exit.
--usage
Print a short usage message and exit.
-V, --version
Display version information.
ENVIRONMENT
MANSECT
If $MANSECT is set, its value is a colon-delimited list of sections and it is used to determine which manual sections to search and
in what order.
MANPATH
If $MANPATH is set, its value is interpreted as the colon-delimited manual page hierarchy search path to use.
FILES
/etc/man_db.conf
man-db configuration file.
/usr/man/index.(bt|db|dir|pag)
A traditional global index database cache.
/var/catman/index.(bt|db|dir|pag)
An alternate or FSSTND compliant global index database cache.
SEE ALSO
man(1), manpath(5), mandb(8)
AUTHOR
Wilf. (G.Wilford@ee.surrey.ac.uk).
Fabrizio Polacco (fpolacco@debian.org).
Colin Watson (cjwatson@debian.org).
2.6.3 2012-09-17 CATMAN(8)