nl command Advent Calendar 2020 This is the last article. I will summarize the direction of the nl command in the future.
GNU coreutils
coreutils has some features that show some future policy.
Coreutils - rejected feature requests
This page contains a list of rejected features. This is to prevent the same feature request from being posted over and over again, even though it has been decided not to do so. nl does not have a feature that has been rejected in the past.
cat -n
RE: cat -n with different format?
Regarding cat -n, it seems that there was a request to change the format of the separator and it was rejected. In response to a request to change the separator to :, the example of awk and grep -n is shown while answering "You can use sed or nl". ~~ There is also an example of nl -s ... ~~
TODO
There is a file called TODO in the coreutils repository, which summarizes what to do in the future. However, there is no item related to nl.
PBRE
nl: add way to exclude matching lines from getting numbered!
In a relatively recent feature proposal, an extension called "PBREthat numbers lines where regular expressions do not match" has been proposed for the numbering methodpBRE` that uses regular expressions. .. But (maybe because I threw it on the bug-coreutils mailing list?) I haven't got a reply so far.
In my personal opinion, it's worth expanding because there are overwhelmingly more opportunities to ** exclude only some lines ** from numbering than to number only some lines. I don't think so. However, I am not confident that there is a need for "only some lines".
If you come up with a plan for yourself, there are three functional improvement plans.
In relation to this article, I think that the slower than cat -n as nl, which specializes in adding line numbers, is a little jeopardized. is. Of course, the short command name and the small number of types are superior, but I feel that the reason for choosing it is a little unattractive.
In connection with this article, it seems unlikely that you will be counting large values as line numbers, but supporting large values is for consistency with other coreutils commands. I think it makes sense. With a recent update, bc and factor now use the GNU MP in all environments. MP is an arbitrary precision calculation library that removes the integer maximum constraint unless memory is exhausted. You may try to implement MP using commands such as seq and nl that can be a source of integers.
In relation to this article, as a result, it became a response to the GNU extension of the -d option, but I wonder if it was actually easier to understand if it was a new independent option. I'm thinking.
*BSD
It seems that the commands have not been improved in BSD including NetBSD.
POSIX
However, from POSIX incompatibility still remains in nl, that will be dealt with before the enhancement.
BusyBox
In BusyBox's nl, the immediate implementation item will be support for" logical pages ". However, the trade-off between "compatibility with rarely used features" and "increased footprint" can be a headache.
Looking at the source, it seems that there are plans to implement a logical page. It seems to be "not implemented yet".
https://github.com/mirror/busybox/blob/master/coreutils/nl.c
static const char nl_longopts[] ALIGN1 =
"body-numbering\0" Required_argument "b"
// "footer-numbering\0" Required_argument "f" - not implemented yet
// "header-numbering\0" Required_argument "h" - not implemented yet
// "section-delimiter\0" Required_argument "d" - not implemented yet
"line-increment\0" Required_argument "i"
// "join-blank-lines\0" Required_argument "l" - not implemented yet
// "number-format\0" Required_argument "n" - not implemented yet
"no-renumber\0" No_argument "p" // no-op so far
"number-separator\0" Required_argument "s"
"starting-line-number\0"Required_argument "v"
"number-width\0" Required_argument "w"
;
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