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Why Learn Awk? (2016)

blog.jpalardy.com

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Re: Why Learn Awk? (2016)

#41

Post by Chris2048 »

rectang wrote: post #28
rhombocombus wrote: post #20

Earlier quoted context omitted.

While I agree that the silent failures and "opaqueness" can be off-putting, once you understand the tool and how to implement it in your workflow it is wonderfully efficient. Aside from being syntactically terse I haven't found any compelling reasons not to use it.

I've achieved a high level of expertise in Perl. Even though I can, I won't write complex Perl one liners; instead, I will write tested, documented utilities which someone who has not achieved such a level of mastery has a shot at grokking, maintaining and debugging. Even better if I can write such utilities in a more modern programming language like Go or Rust, if the organization has personnel with expertise in suc…

What if the task is one-off? would you still care to write a proper utility?

As an example, you have some data you need to fix as input to some program. you incrementally try to fix it with perl:

1) run program with data, observe errors, infer what needs fixing ->

2) write perl to fix data, modify data ->

3) repeat from (1) until no errors

You have no expectation you'll ever need to fix data corrupted in the same way ever again.

Re: Why Learn Awk? (2016)

#44

Post by syncsynchalt »

cauthon wrote: post #34
jerf wrote: post #9

Because for some bizarre reason, "cut" doesn't ship with any decent column selection logic that is the equivalent of awk's $1, $2, etc., even in 2020. That's like 90% of my use of awk right there. I don't know of any easier equivalent of "awk '{ print $2 }'" for what it does. Posted partially so the Internet Correction Squad can froth at the mouth and set me straight, because I'd love to be showed to be wrong here.

> I don't know of any easier equivalent of "awk '{ print $2 }'" for what it does. Does `cut -f2` not work? My complaint with cut is that you can't reorder columns (e.g. `cut -f3,2` ) Awk is really great for general text munging, more than just column extraction, highly recommend picking up some of the basics Edit to agree with the commenters below me: If the file isn't delimited with a single character, then cut alon…

It does not. Compare:

    $ echo '   1     2   3' | cut -f2
       1     2   3
    $ echo '   1     2   3' | cut -f2 -d' '
    
    $ echo '   1     2   3' | awk '{print $2}'
    2
"-f [...] Output fields are separated by a single occurrence of the field delimiter character."

Re: Why Learn Awk? (2016)

#45

Post by cauthon »

ColinWright wrote: post #37
Scarbutt wrote: post #18

Earlier quoted context omitted.

And awk doesn't offers cut's column range selection ;)

I'm an expert on neither AWK nor cut , but AWK allows you to select a field, or the entire line, and then substrings within those. Select characters 3-6 (inclusive) in the second field: $ echo Testing LengthyString | awk '{print substr($2,3,4)}' > ngth If you want to select columns from the entire line, then: $ echo Testing LengthyString | awk '{print substr($0,3,4)}' > stin Is that what you meant?

I don't think so. I think they're referring to cut's ability to select an arbitrary range of columns, e.g. `cut -f 2-7` to select the 2nd through 7th columns, while awk requires you to explicitly enumerate all desired columns, i.e. `awk '{print $2, $3, $4, $5, $6, $7}'

Re: Why Learn Awk? (2016)

#46

Post by jolmg »

cauthon wrote: post #34
jerf wrote: post #9

Because for some bizarre reason, "cut" doesn't ship with any decent column selection logic that is the equivalent of awk's $1, $2, etc., even in 2020. That's like 90% of my use of awk right there. I don't know of any easier equivalent of "awk '{ print $2 }'" for what it does. Posted partially so the Internet Correction Squad can froth at the mouth and set me straight, because I'd love to be showed to be wrong here.

> I don't know of any easier equivalent of "awk '{ print $2 }'" for what it does. Does `cut -f2` not work? My complaint with cut is that you can't reorder columns (e.g. `cut -f3,2` ) Awk is really great for general text munging, more than just column extraction, highly recommend picking up some of the basics Edit to agree with the commenters below me: If the file isn't delimited with a single character, then cut alon…

Not if the columns are separated by variable number of spaces. By default, the delimiter is 1 tab. You can change it to 1 space, but not more and not a variable number.

In my experience, most column based output uses variable number of spaces for alignment purposes. Tabs can work for alignment, but they break when you need more than 8 spaces for alignment.

Re: Why Learn Awk? (2016)

#47

Post by cauthon »

syncsynchalt wrote: post #44
cauthon wrote: post #34

Earlier quoted context omitted.

> I don't know of any easier equivalent of "awk '{ print $2 }'" for what it does. Does `cut -f2` not work? My complaint with cut is that you can't reorder columns (e.g. `cut -f3,2` ) Awk is really great for general text munging, more than just column extraction, highly recommend picking up some of the basics Edit to agree with the commenters below me: If the file isn't delimited with a single character, then cut alon…

It does not. Compare: $ echo ' 1 2 3' | cut -f2 1 2 3 $ echo ' 1 2 3' | cut -f2 -d' ' $ echo ' 1 2 3' | awk '{print $2}' 2 "-f [...] Output fields are separated by a single occurrence of the field delimiter character."

oh yes, totally agree. if the data isn't delimited by a single character, then you definitely need awk or sed+cut

Re: Why Learn Awk? (2016)

#48

Post by jandrese »

Chris2048 wrote: post #21

Hmm. I'm sure this question will induce a flamewar of practical "#NeverAwk"-ers fighting toolbelt bloat, versus tech-hoarding AWK apologists arguing against throwing something out given if fills . Here's the thing: these arguments all too commonly focus on subjective notions of "simplicity", and toy examples divorced from actual common practise, and or solid comparable benchmarks . Show me a range of practical exampl…

I sat down and read through the Awk manual once just to learn and was pleasantly surprised at how orthogonal the language is and how much it offers.

The only problem is that it was written by people using ed on PDP computers and that kind of shows. The primary logic is "filter out lines X and apply transform Y" is completely natural to someone using an editor like ed, but is fairly foreign to modern computer users. Most people aren't going to take the time to learn an obscure commandline tool these days, especially since it comes from the Dennis Ritchie school of "errors are like angry housewives, you know what you did" debugging.

Re: Why Learn Awk? (2016)

#49

Post by shpeedy »

rhombocombus wrote: post #14

It is fast, robust, and frequently far more performant than a lot of modern tools that can be overkill for most data manipulation. I use it all the time in our ETL processes and it always works as advertised.

Perl is much faster[0], with much more features, with bunch of ready to use libraries, with package manager (CPAN), and similar syntax to awk.

Why you use awk?

[0]: http://rc3.org/2014/08/28/surprisingly-perl-outperforms-sed-...

Re: Why Learn Awk? (2016)

#50

Post by chrisjc »

iagovar wrote: post #38
samatman wrote: post #25

> Imagine programming without regular expressions. I live in this future and it's beautiful. Steps to programming without regular expressions: 1) find a PEG library for your language of choice There is no step 2.

Sorry for asking such dub question, but what's a PEG library?

No idea... had to look it up. Parsing Expression Grammar.

https://en.wikipedia.org/wiki/Parsing_expression_grammar

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