Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Use long flags when scripting

thechangelog.com

Post reply on HN
Print view View original

101–110 of 133 posts

Re: Use long flags when scripting

#101

Post by kragen »

danielvinson wrote: post #97
rlpb wrote: post #67

Earlier quoted context omitted.

> This is not the bread and butter of programming... This is, however, the bread and butter of shell programming. > ... "tr --delete --complement"... And, likewise, I'm not sure of the meaning of --delete and --complement, but I do understand "tr -dc". I'd have to look up --delete and --complement to work out what they're the equivalent of.

"This is, however, the bread and butter of shell programming." This is really old-fashioned thinking. The people who have been in this industry for 10+ years all grew up without computers - and thus had to memorize all of the flags, obscure shell commands, and weird regular expression. What was taught in school back then was to do things perfectly the first time, because CPU cycles were expensive, and bugs were time…

You're going to have a hard time making it through Hemingway if you have to reach for a dictionary every time you come across a word like "middleweight" or "khaki", even if your dictionary is online and answers your query in less than a second. You need to memorize the meanings of a vocabulary of words in order to read fluently or write well. That's not "old-fashioned thinking". It's just common sense. And it's just as true of shell scripts as it is of electrical engineering, mechanical engineering, poetry, or math.

Re: Use long flags when scripting

#102

Post by reledi »

npsimons wrote: post #78
jsaxton86 wrote: post #62

Earlier quoted context omitted.

A much simpler solution is to comment your code: # Invoke curl in silent mode (-s), pipe the output to grep # and use an extended regex (-E) to only show the resulting # digits (-o: only print matching text, not the whole line): curl -s checkip.dyndns.org | grep -Eo '[0-9\.]+'

I don't like commenting the how and what; that's what the code is for. Comments are for "why".

How and what are good to include when describing the function, but not for specific statements of code.

Re: Use long flags when scripting

#105

Post by mbillie1 »

peatfreak wrote: post #91
dasil003 wrote: post #85

Earlier quoted context omitted.

I'm all for being nice, but I think you are missing the point. It's not about flexing knowledge for ego's sake, that's entirely beside the point. No, the source of Unix nerd's retort is the realization that a small set of simple, standardized and very sharp tools performs better over time than an ever-increasing set of intuitive tools to suit a narrow use case. This is not to disparage anyone for writing something li…

> a small set of simple, standardized and very sharp tools This may have been true(r) twenty or thirty years ago, but in a contemporary Unix installation, it is not true at all. The set of tools is often NOT small (there are thousands of them); they are NOT simple (two examples: 1. the ls man page and the huge number of options it takes; 2. shell quoting rules); they are NOT standardized (I regularly run into incompa…

I would respectfully disagree here. I can't remember, and won't bother to look up, how to recursively use cp / mv / scp / rsync / whatever else... but I'd bet it's -r, or -R. I'm not positive how to tell a shell program "I REALLY MEAN IT!", but I''d guess it's -f (unless it's kill, and I'm not going to sympathize with gripers over that one odd case :) ). There really is an (admittedly idiomatic, but still present) intuitive nature to these things. There are loads of counterexamples, for sure. But still - say I want to use extended Regexp in grep, or sed. I bet it's "-e" or "-E", right? Plus you can always search the man-page, without bothering to read it all.

Reading man-pages does do a lot for you. And in my experience, I don't spend a lot of time while on the same engagement/project/whatever writing shell code across BSD/solaris/GNU-linux/etc.

And honestly, if you can write a sophisticated sed substitution for BSD without reading the man page, is there really THAT big of a barrier lying between you and writing the same thing in GNU/Linux, or non-POSIX-compliant sed, or whatever else? You read the man page for 10 seconds and find the flag that means what you want to use. If it's different, you explore.

This is totally not a rant at you, and I sincerely hope you don't take it that way - I just haven't found myself utterly foiled by the differences between say, RHEL v SUSE v BSD recently. There are differences, but hell - there are differences between versions of languages, between terminal emulators (scripts that work in bash but not in zsh and vice versa), etc.

Re: Use long flags when scripting

#106

Post by mbillie1 »

sirclueless wrote: post #66
ralph wrote: post #42

This is very bad advice. I won't thank you for making me check GNU grep's --ignore-case is precisely the same as the very well-known, POSIX'd, -i. And ditto for all the other verbiage that clutter and obfuscate the script's intent. Short options should be used where they're the more typically known and standardised. Long options are for the unusual. grep -iv sed -n tr -dc awk -f ls -tr comm -23 tail -n

I'm a 4th year student in a well-respected CS program, I have used linux off and on for over three years now, and I would consider myself perfectly capable of maintaining a shell script using any of the utilities you mention. However, without checking the man pages I could not tell you the behavior of the -n flag for sed, the -dc flags for tr, the -f flag for awk, or the -tr flags for ls, and I only have a guess as t…

If you aren't sure what the "-" flag does for a particular command, but you are a competent Unix user, you should be fine with the man page or 10 seconds of Google. If you aren't used to Unix, then I think it's dangerous to expect the verbose flags to explain things simply to you. For example, what would --mmap or --null-data mean to you in the context of the grep command? Are they immediately obvious?

Re: Use long flags when scripting

#107

Post by eric-hu »

ralph wrote: post #53
skrebbel wrote: post #51

Earlier quoted context omitted.

The difference is that with long flags, even someone without 10 years of POSIX experience knows what's going on. The long example on the OP's article makes a lot of sense to me, even though I'm primarily a Windows user. At the same time, for instance, I've no idea what the -tr flag to ls does, even though I use ls often enough.

You are not a Unix user. You don't know Unix's commands and their common options. If the article is aimed at you and people like you that read your scripts then it's fine but it's akin to commenting "dir /w" in a DOS batch file to explain its purpose. Unix users should not following the article's advice, they should be embracing Unix's style and ethos; it's part of what's made it such a success. BTW, a month of using…

Is Randall Munroe a Unix user after 15 years of using it?

http://xkcd.com/1168/

Re: Use long flags when scripting

#108

Post by darrikmazey »

My age probably shows in this statement, but it seems odd to me to suggest that someone else change their behaviour so the poster does not have to rtfm. We're coders. When we don't understand something, we read the manual, then the source.

Re: Use long flags when scripting

#109

Post by mbillie1 »

eric-hu wrote: post #107
ralph wrote: post #53

Earlier quoted context omitted.

You are not a Unix user. You don't know Unix's commands and their common options. If the article is aimed at you and people like you that read your scripts then it's fine but it's akin to commenting "dir /w" in a DOS batch file to explain its purpose. Unix users should not following the article's advice, they should be embracing Unix's style and ethos; it's part of what's made it such a success. BTW, a month of using…

Is Randall Munroe a Unix user after 15 years of using it? http://xkcd.com/1168/

That's a comic. He sells a shirt on his site's store that is filled with Unix tips, including "tar -xf # extract anything". I'm not sure this is a legitimate criticism.

Re: Use long flags when scripting

#110

Post by mbillie1 »

ralph wrote: post #42

This is very bad advice. I won't thank you for making me check GNU grep's --ignore-case is precisely the same as the very well-known, POSIX'd, -i. And ditto for all the other verbiage that clutter and obfuscate the script's intent. Short options should be used where they're the more typically known and standardised. Long options are for the unusual. grep -iv sed -n tr -dc awk -f ls -tr comm -23 tail -n

And at least a few of these (grep -iv, sed -n, ls -tr) aren't even unusual. If you ask what -iv means in grep, I assume you have used grep < 10 times ever.
Post reply on HN