编程与软件工程ferd.ca编辑精选
20 分钟学会 Awk（2015）
Awk in 20 Minutes (2015)
2015 — 2024，它一次次回到首页
黑点是上首页（≥ 50 分）的那次投稿，空心点是没冲上去的投稿，点越大分数越高。
导读
这篇文章试图用 20 分钟讲清 awk 的核心用法，面向想快速上手命令行文本处理的人。它把 awk 当作一种小而够用的工具来介绍，适合在需要时快速重读、捡回记忆。
为什么经久不衰：awk 小到能装进脑子，隔几年花 20 分钟就能重新掌握；对基础文本处理来说，它比大型语言更简单、更不容易写错。
HN 评论精选
awk 因小而可掌握、可快速重学，基础文本处理比 Perl 更不易写错；但不同 awk 实现的边角行为有差异。
我在大学时（Perl 5.6 时代）学 Perl，曾用它做大量文本处理。后来我硬着头皮学了 awk，结果基本弃用了 Perl。为什么？awk 足够小，能装进我脑子里，至少我每隔几个月要用到的那部分能；忘了也没关系，花 20 分钟就能捡回来。相比之下 Perl 太大，装不进脑子，生态还要大得多。我知道 Perl 能做我用 awk 做的事，但对基础任务来说，awk 几乎就是逐行处理输入并条件执行，所以能出错的方式少得多。注意：awk、nawk、mawk、gawk 的边角情况不一定相同，碰到不熟悉的实现时错误信息未必看得懂。
mauvehaus查看英文原文
I learned perl in college in the 5.6 days, and did a lot of text processing with it for a time. At some point, I bit the bullet and learned awk, and I've mostly abandoned perl as a result. Why? awk is small enough that it fits in my head, or at least the bits I need every couple of months do. And if I forget, it only takes 20 minutes to put them back in. perl, by contrast, is far too large to fit in my head and comes with an ecosystem that is much larger still. I know I can use perl for what I use awk for, and when I've raised this point before, people have been quick to explain how to process input by lines, and conditionally do something. For basic stuff, the fact that that's basically all awk does[0] means there's so many fewer ways to do it wrong. I can't say the same of perl, even when I was more familiar with it. caveat: awk, nawk, mawk, and gawk don't necessarily share the same set of corner cases, and you may not get error messages that make sense to you when you bump into one with an unfamiliar awk. [0] I know, not really, and especially for gawk. I've written awk scripts a couple hundred lines in the past. It's true enough for the 20 minute version though. Edited for clarity.
awk 适合写小巧、贴合问题的计算/文本处理程序，Ward Cunningham 的费用分摊器是范例。
我最喜欢的 awk 能力示例是 Ward Cunningham 的这个计算器，用来分摊滑雪旅行费用。代码短小漂亮，很适合这个问题：https://c2.com/doc/expense/
liammonahan查看英文原文
My absolute favorite example of what's possible with awk is this[0] calculator from Ward Cunningham about splitting expenses on a ski trip. It's a really beautiful little piece of code well-adapted to this problem. [0] - https://c2.com/doc/expense/
评论者称赞文章覆盖了要点，并给出自己的 awk 演讲与练习资源供深入学习。
这篇博文很棒，我会推荐给别人！重要点都讲到了。如果想更深入、全面地探索 awk，我最近在 Linux Fest Northwest 2020 做过一个线上演讲，并配有练习和 GitHub 仓库。
freedomben查看英文原文
This is an excellent blog post. I will refer people to this! He touches on all of the important points. If you want a more thorough/deep exploration of Awk, I recently gave a talk on it (virtually) at Linux Fest Northwest (LFNW) 2020. Awk: Hack the planet['s text]! Part 1 (Presentation): https://www.youtube.com/watch?v=43BNFcOdBlY Awk: Hack the planet['s text]! Part 2 (Exercises):https://www.youtube.com/watch?v=4UGLsRYDfo8 If you want to try your hand at the exercises, they are on github: https://github.com/FreedomBen/awk-hack-the-planet
awk 通过把未传入的多余形参初始化为零来模拟局部变量，这是常见写法。
也值得提一下：可以用额外的形参来模拟局部变量。在 awk 中，函数调用里缺失的参数会被初始化为零。比如 CharCount(ch, line, n) 中，参数列表里的换行是 awk 惯例，表示 n 是“局部变量”。
augustk查看英文原文
It's also worth mentioning that local variables can be simulated using additional formal parameters. In AWK, any missing parameter in a function call is initialized to zero. Let's say we have a function CharCount which takes a character and a line of text and returns the number of occurrences of that character: function CharCount(ch, line, n) { ... } The line break in the parameter list is an AWK convention and indicates that n is a "local variable."
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