4 ms·

>Your "shell" solution isn't really a shell solution, it's an awk solution. >It's really valuable to know awk, but it's a bit misleading to claim that "it's sh

by vram22 8y ago

>Your "shell" solution isn't really a shell solution, it's an awk solution. >It's really valuable to know awk, but it's a bit misleading to claim that "it's shell". It's more than a bit misleading to accuse someone of being misleading, without checking your facts first. Maybe you spoke too soon, without reading the full post, as I find people sometimes (often?) do (not just in reply to my comments, but to those of others too), not just on HN, but on many forums. Read both the header comment and the last line of the script you called "an awk solution": Header comment: # bentley_knuth.sh Of course, the filename extension does not make it a shell solution instead of an awk solution, but I used .sh because I knew what I was doing [1]. See next point. Last line of that script: ' < $2 | sort -nr +1 | sed $1q So the script uses all of awk, sort, sed and shell - which you seem to have missed, maybe because you only skimmed the first some lines before replying here. That makes it a shell script in my book, plus see below. The $2 and the $1 - in the $1q bit - are shell command line parameters, because this code is invoked from the shell as a script, with arguments passed. Also see the pipe symbols (|). All these are part of shell syntax, not awk syntax (although awk has $1, $2, etc. too, they have a different, though related meaning - in fact, I use a $i in my awk script within this shell script too). The whole script is a pipeline, that pipes the awk script's output to sort and sort's to sed. I don't know if you are a shell/awk newbie or not, but regardless, you missed those points above, like I said, probably due to haste. [1] Check out this recent article by me in Linux Pro Magazine: http://www.linux-magazine.com/Issues/2018/217/Exploring-proc http://www.linux-magazine.com/Issues/2018/217/Exploring-proc for a bit of shell quoting magic along with some use of awk. And this post: UNIX one-liner to kill a hanging Firefox process: https://jugad2.blogspot.com/2008/09/unix-one-liner-to-kill-hanging-firefox.html https://jugad2.blogspot.com/2008/09/unix-one-liner-to-kill-h... and also the interesting comments on that post, from which I learned some things. After having worked for years on Unix platforms (as both a dev and system engineer), from even before Linux was created, I think I know the difference between shell and awk (and a bit more, although still do not claim to know everything, or even close). On a more positive note, I'll use this as an opportunity to put in a plug for my Python and Linux training offerings :) Course outlines and a couple of testimonials here: https://jugad2.blogspot.com/p/training.html https://jugad2.blogspot.com/p/training.html

CarolineW 8y ago
I read your entire post, and I didn't miss any of the points you make. I simply disagree with you. Quoting from your post: And here is my initial solution in UNIX shell: # bentley_knuth.sh # Usage: # ./bentley_knuth.sh n file # where "n" is the number of most frequent words # you want to find in "file". awk ' { for (i = 1; i <= NF; i++) word_freq[$i]++ } END { for (i in word_freq) print i, word_freq[i] } ' < $2 | sort -nr +1 | sed $1q So you invoke awk, and then run the output of awk through sort and sed. You're doing all the word counting in awk. Yes, you're invoking awk from a shell script, but that's really not the same thing as "using shell." McIlroy’s solution is genuinely shell: tr -cs A-Za-z ' ' | tr A-Z a-z | sort | uniq -c | sort -rn | sed ${1}q "awk" is generally accepted as a full programming language, whereas "tr", "sort", "uniq", and "sed" are command line utilities. I don't think "awk" classes as a command line utility, so I don't class your solution as "shell". Perhaps you don't agree, perhaps you think "awk" is a command line utility. If so, then we'll agree to disagree.
- vram22 8y ago
  Wow. Multiple misunderstandings on your part in one single fairly short comment. I'll of course reply to it, substantiating what I said, as best as I can, but it's late here, and when replying to an argument, I prefer to do it thoroughly enough, so I'll do it, hopefully, by tomorrow night my time, otherwise a day later, if too busy. I think the reply link should be alive until then. Meanwhile, you might want to scrutinize your own reply (the one to which I am replying here) and think a bit more deeply about what might be wrong with it. And until my full reply to come later, here are a couple of hints: Hint 1: >"awk" is generally accepted as a full programming language, whereas "tr", "sort", "uniq", and "sed" are command line utilities. - a tool can very much be both a full programming language as well as a command line utility at the same time. awk falls into that category [1], as do many other Unix commands. Who made up a rule that it cannot be both at the same time? You? Hint 2: Check out your line: >So you invoke awk, and then run the output of awk through sort and sed. and compare and contrast its meaning with the meaning of your few lines immediately below it, including the one that says "McIlroy’s solution is genuinely shell:". Try to see the similarity/difference/contradiction. [1] Finally, read the book The Unix Programming Environment, a classic, by Kernighan and Pike (Unix pioneers). I cut my Unix teeth on it, years ago, although, of course, years do not mean I am right and you are wrong. Facts do. There are chapters in the book on awk and sed. And IIRC they come under the topic of filters (maybe even the chapter name is that) a.k.a. command-line utilities, although not every such utility needs to be, or is, a filter. I think you have some confusion about terms and their meanings, and/or are assigning your own meaning, even though you use words like "generally accepted". Also skim this article (published by me, years ago, on IBM developerWorks) to get your fundamentals more clear: Developing a Linux command-line utility: https://jugad2.blogspot.com/2014/09/my-ibm-developerworks-article.html https://jugad2.blogspot.com/2014/09/my-ibm-developerworks-ar... Enough for today - will do follow-up comment as I said, if needed, in a day or two.

by vram22 8y ago

CarolineW 8y ago

I read your entire post, and I didn't miss any of the points you make. I simply disagree with you. Quoting from your post: And here is my initial solution in UNIX shell: # bentley_knuth.sh # Usage: # ./bentley_knuth.sh n file # where "n" is the number of most frequent words # you want to find in "file". awk ' { for (i = 1; i <= NF; i++) word_freq[$i]++ } END { for (i in word_freq) print i, word_freq[i] } ' < $2 | sort -nr +1 | sed $1q So you invoke awk, and then run the output of awk through sort and sed. You're doing all the word counting in awk. Yes, you're invoking awk from a shell script, but that's really not the same thing as "using shell." McIlroy’s solution is genuinely shell: tr -cs A-Za-z ' ' | tr A-Z a-z | sort | uniq -c | sort -rn | sed ${1}q "awk" is generally accepted as a full programming language, whereas "tr", "sort", "uniq", and "sed" are command line utilities. I don't think "awk" classes as a command line utility, so I don't class your solution as "shell". Perhaps you don't agree, perhaps you think "awk" is a command line utility. If so, then we'll agree to disagree.

vram22 8y ago
Wow. Multiple misunderstandings on your part in one single fairly short comment. I'll of course reply to it, substantiating what I said, as best as I can, but it's late here, and when replying to an argument, I prefer to do it thoroughly enough, so I'll do it, hopefully, by tomorrow night my time, otherwise a day later, if too busy. I think the reply link should be alive until then. Meanwhile, you might want to scrutinize your own reply (the one to which I am replying here) and think a bit more deeply about what might be wrong with it. And until my full reply to come later, here are a couple of hints: Hint 1: >"awk" is generally accepted as a full programming language, whereas "tr", "sort", "uniq", and "sed" are command line utilities. - a tool can very much be both a full programming language as well as a command line utility at the same time. awk falls into that category [1], as do many other Unix commands. Who made up a rule that it cannot be both at the same time? You? Hint 2: Check out your line: >So you invoke awk, and then run the output of awk through sort and sed. and compare and contrast its meaning with the meaning of your few lines immediately below it, including the one that says "McIlroy’s solution is genuinely shell:". Try to see the similarity/difference/contradiction. [1] Finally, read the book The Unix Programming Environment, a classic, by Kernighan and Pike (Unix pioneers). I cut my Unix teeth on it, years ago, although, of course, years do not mean I am right and you are wrong. Facts do. There are chapters in the book on awk and sed. And IIRC they come under the topic of filters (maybe even the chapter name is that) a.k.a. command-line utilities, although not every such utility needs to be, or is, a filter. I think you have some confusion about terms and their meanings, and/or are assigning your own meaning, even though you use words like "generally accepted". Also skim this article (published by me, years ago, on IBM developerWorks) to get your fundamentals more clear: Developing a Linux command-line utility: https://jugad2.blogspot.com/2014/09/my-ibm-developerworks-article.html https://jugad2.blogspot.com/2014/09/my-ibm-developerworks-ar... Enough for today - will do follow-up comment as I said, if needed, in a day or two.