linux

a while ago, i blogged about uploading files to s3 using curl and provided the solution as two functions written in bash, and basically the only feedback was “wait. you can write functions in bash?”

you can. but in reality, you probably don’t want to. the syntax for defining (and calling) bash functions is horrible. there’s a reason people genrally don’t use them. writing and using functions in amber, by comparison, is a borderline delight of sanity. if you’ve ever written a function in php or python or javascript, amber’s function syntax will feel familiar and, well, ‘normal’.

a programming language is only ever going to be as good as its standard library. try writing a c program without <string.h>, for instance . it’s not great.

amber’s standard library is not large — it’s only 24 commands, and some of those aren’t yet available in version 1.0 — but it provides a lot of the convenience functionality that we want when scripting. there’s string manipulation, array handling, some file access stuff. all of these functions are, under the hood, just bash commands, but they provide proven and convenient ways to do the things we want to do.

none of the standard library commands are covered in the official documentation. to find out what they do (or even that they exist), you need to read the source code. so, lets’ go over them here so we don’t have to do that.

in this series we’re looking at using the amber language to write scripts that transpile into bash. so far we’ve covered using shell commands and handling error cases. in this installment, we’ll be looking at control structures: loops and ifs, basically.

writing shell scripts is zero fun. the bash syntax is a mess, error handling is difficult, and any script longer than a hundred lines is basically unreadable. but we keep writing bash scripts because they’re the right tool for the job and the job must be done.

amber aims to fix this pain by being a language that gives us a sane, readable syntax that transpiles into messy bash so we don’t have to write messy bash ourselves.

this post is a four-parter that will go over the basic features of amber from the perspective of those of us who actually want to use it. we’ll start with calling shell commands and handling errors, then look at loops and if statements, the standard library of commands, and finally investigate functions.

there are times when we tar and gzip a directory and the final tarball is just too damn big. maybe it doesn’t fit on any of those old thumbdrives we got at the 7-eleven, or maybe we’re trying to upload it to s3 and aws is complaining it’s too large.

let’s take a look at a quick and dirty way to split our tarballs into a bunch of smaller files of a set size.

a week ago, i ran this db insert-heavy script on a server and forgot to turn off mysql‘s binlog feature first. the result, of course, is that i filled up the disk in about three minutes and brought the whole server down. not great for a tuesday. fortunately, finding and fixing the problem was straightforward. the downtime was only a couple of minutes.

in this post we’re going to go over inspecting our disk space; figuring out how much we have left and finding out what we spent all those blocks on. we’ll look at three basic tools:

df for inspecting disk space
du for getting directory sizes
find for finding files to delete these all come pre-packaged with your linux or linux-like operating system, so put that apt back in your pocket.