{"id":859,"date":"2020-02-08T18:27:21","date_gmt":"2020-02-08T18:27:21","guid":{"rendered":"http:\/\/www.vidarholen.net\/contents\/blog\/?p=859"},"modified":"2020-02-09T06:30:56","modified_gmt":"2020-02-09T06:30:56","slug":"lessons-learned-from-writing-shellcheck-githubs-now-most-starred-haskell-project","status":"publish","type":"post","link":"https:\/\/www.vidarholen.net\/contents\/blog\/?p=859","title":{"rendered":"Lessons learned from writing ShellCheck, GitHub’s now most starred Haskell project"},"content":{"rendered":"\n

ShellCheck<\/a> is a static analysis tool that\npoints out common problems and pitfalls in shell scripts.<\/p>\n

As of last weekend it appears to have become GitHub’s most starred Haskell\nrepository<\/a>,\nafter a mention in MIT SIPB’s Writing Safe Shell\nScripts<\/a> guide.<\/p>\n

While obviously a frivolous metric in a niche category, I like to interpret this\nas meaning that people are finding ShellCheck as useful as I find\nPandoc<\/a>, the excellent universal document converter I use\nfor notes, blog posts and ShellCheck’s man page, and which held a firm grip on\nthe top spot for a long time.<\/p>\n

I am very happy and humbled that so many people are finding the project helpful\nand useful. The response has been incredibly and overwhelmingly positive.\nSeveral times per week I see mentions from people who tried it out, and it\neither solved their immediate problem, or it taught them something new and\ninteresting they didn’t know before.<\/p>\n

I started the project 8 years ago, and this seems like a good opportunity to\nshare some of the lessons learned along the way.<\/p>\n

Quick History<\/h3>\n

ShellCheck is generally considered a shell script linter, but it actually\nstarted life in 2012 as an IRC bot (of all things!) on #bash@Freenode. It’s\nstill there and as active as ever.<\/p>\n

The channel is the home of the comprehensive and frequently cited Wooledge\nBashFAQ<\/a>, plus an additional list of\ncommon pitfalls<\/a>. Between them, they\ncurrently cover 178 common questions about Bash and POSIX sh.<\/p>\n

Since no one ever reads the FAQ, an existing bot allowed regulars to e.g.\nanswer any problem regarding variations of for file in `ls`<\/code><\/a> with a simple !pf 1<\/code>, and\nlet a bot point the person in the right direction (the IRC equivalent of\nStackOverflow’s "duplicate of").<\/p>\n

ShellCheck’s original purpose was essentially to find out how many of these\nFAQs could be classified automatically, without any human input.<\/p>\n

Due to this, ShellCheck was designed for different goals than most linters.<\/p>\n

    \n
  1. It would only run on buggy scripts, because otherwise they wouldn’t have been posted.<\/li>\n
  2. It would only run once, and should be as helpful as possible on the first pass.<\/li>\n
  3. It would run on my machine, not on arbitrary user’s systems.<\/li>\n<\/ol>\n

    This will become relevant.<\/p>\n

    On Haskell<\/h3>\n

    Since ShellCheck was a hobby project that wasn’t intended to run on random\npeople’s machines, I could completely ignore popularity, familiarity, and\npracticality, and pick the language that was the most fun and interesting.<\/p>\n

    That was, of course, Haskell.<\/p>\n

    As anyone who looks at code will quickly conclude, ShellCheck was my first real\nproject in the language.<\/p>\n

    Some things worked really well:<\/p>\n