blog: new post: The Beautiful in the Ugly

blog/beauty-in-ugly-2018-04-23.markdown

@@ -0,0 +1,88 @@
+---
+title: The Beautiful in the Ugly
+date: 2018-04-23
+for: Silver
+---
+
+# The Beautiful in the Ugly
+
+Functional programming is nice and all, but sometimes you just need to have
+things get done regardless of the consequences. Sometimes a dirty little hack
+will suffice in place of a branching construct. This is a story of one of these
+times.
+
+In shell script, bare words are interpreted as arbitrary commands for the shell
+to run, interpreted in its rules (simplified to make this story more interesting):
+
+1. The first word in a command is the name or path of the program being loaded
+2. Variable expansions are processed before commands are executed
+
+Given the following snippet of shell script:
+
+```shell
+#!/bin/sh
+# hello.sh
+
+function hello {
+  echo "hello, $1"
+}
+
+$1 $2
+```
+
+When you run this without any arguments:
+
+```console
+$ sh ./hello.sh
+$
+```
+
+Nothing happens.
+
+Change it to the following:
+
+```console
+$ sh ./hello.sh hello world
+hello, world
+$ sh ./hello.sh ls
+hello.sh
+```
+
+Shell commands are bare words. Variable expansion can turn into execution.
+Normally, this is terrifying. This is useful in fringe cases.
+
+Consider the following script:
+
+```shell
+#!/bin/sh
+# build.sh <action> [arguments]
+
+projbase=github.com/Xe/printerfacts
+
+function gitrev {
+  git rev-parse HEAD
+}
+
+function app {
+  export GOBIN="$(pwd)"/bin
+  go install github.com/Xe/printerfacts/cmd/printerfacts
+}
+
+function install_system {
+  app
+  
+  cp ./bin/printerfacts /usr/local/bin/printerfacts
+}
+
+function docker {
+  docker build -t xena/printerfacts .
+  docker build -t xena/printerfacts:"$(gitrev)"
+}
+
+function deploy {
+  docker tag xena/printerfacts:"$(gitrev)" registry.heroku.com/printerfacts/web
+  docker push registry.heroku.com/printerfacts/web
+}
+
+$*
+```