Why VIM?
Sooner or later there comes the day when your easy-to-use IDE becomes useless for handling huge files. There aren’t many editors capable of working with very large files, like production logs for instance.
I’ve recently had to analyze a 100 MB one-line JSON file and once more VIM saved the day. VIM, like many other Unix utilities, is both tough and brilliant. Git interactive rebase requires you to know it, and if you’re still not convinced, maybe this great article will make you change your mind.
Let’s see how easily you can pretty print a JSON file with VIM. First we will download a one-line JSON file from Reddit.
$ wget http://www.reddit.com/r/programming.json --2014-01-24 12:21:04-- http://www.reddit.com/r/programming.json Resolving www.reddit.com (www.reddit.com)... 77.232.217.122, 77.232.217.113 Connecting to www.reddit.com (www.reddit.com)|77.232.217.122|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 28733 (28K) [application/json] Saving to: `programming.json' 100%[======================================>] 28,733 --.-K/s in 0.03s 2014-01-24 12:21:04 (1021 KB/s) - `programming.json' saved [28733/28733]
This is how it looks like:
Pretty printing
Python comes along with most Unix distributions, so running the following VIM command manages to do the trick:
%!python -m json.tool
Let’s save the pretty printed JSON file and put other Unix tools to work.
:w programming_pretty.json
Matching time
Let’s say we want to extract all “domain” related values:
"domain": "mameworld.info"
Sed to the rescue
$ sed -nr 's/^.*"domain":\s*"(.*?)".*$/\1/p' <programming_pretty.json | sort -u blog.safaribooksonline.com chadfowler.com cyrille.rossant.net dot.kde.org evanmiller.org fabiensanglard.net galileo.phys.virginia.edu github.com halffull.org ibuildings.nl jaxenter.com jobtipsforgeeks.com kilncode.com libtins.github.io mameworld.info miguelcamba.com minuum.com notes.tweakblogs.net perfect-pentago.net periscope.io reuters.com tech.blog.box.com tmm1.net vocalbit.com youtube.com
Multi-line matching
Sed is line oriented, and while it offers multi-line support, it’s no match for perl. Let’s say I want to match all authors in the following JSON pattern:
"data": {
"author": "justrelaxnow",
}This is how I do it:
$ perl -0777 -n -e 'print "$2\n" while (m/("data":\s*\{.*?"author":\s*"(.*?)"[,|\s*\}].*?\},)/sgmp)' programming_pretty.json | sort -u
AmericanXer0
azth
bionicseraph
bit_shiftr
charles_the_hard
Gexos
jakubgarfield
johnwaterwood
joukoo
justrelaxnow
Kingvash
krets
mariuz
mopatches
nyphrex
pseudomind
rluecke3
sltkr
solidus-flux
steveklabnik1
sumstozero
swizec
vocalbit
WolfspawConclusion
Unix tools are old school, some of those being written forty years ago. The learning curve might be steep, but learning them is a great investment. A great software library stands the test of time and Unix tools are a good reminder that tough jobs call for tough tools.
You don’t have to use vim for interactive rebase in git, see GIT_EDITOR or core.editor configuration properties. Moreover in order to format JSON using Python script you don’t have to open that file in vim in the first place. You can simply pipe file to script and then pipe results to second file.
Indeed you don’t need VIM for git or for formatting json. That vim command is actually calling python to do its job. But VIM is installed almost anywhere and it’s worth knowing its basics.
So much fail. 1. I didn’t see a single justification for dragging Vim into this article. 2. Vim is running on my Windows PC so it is not like it is specific to Unix. 3. The sed expression is overly complicated. There is no need to aanchor the expression with ^ and $. 4. FINDSTR (on Windows) combined with an FOR /F loop to tokenize the output would have done the same job. Again, not specifically Unix. 5. Perl (and) have been ported to Windows, so again, not really Unix-specific. No, the take-away here is to use the best tool… Read more »
I used all those tools on windows, yet they are still Unix tools. Once learned you can use them on any OS these days, so it’s really useful to know them. 1. Vim manages to open a 1GB XML file, which I can grep/sed or do anything I want with it. How many IDEs can do that? 2. I ran Vim on windows and yes it is a Unix tool. 3. I want an exact match that’s why I used the ^ and $. 4. FINDSTR and FOR/F windows batching is the “poor man’s batch utilities”. For OS independent batch… Read more »