Inject

Inject is a little shell redirection utility that allows you to substitute piped input anywhere into a string, then run it as a command or print it to the console. Here's what I mean:

$ echo -n "hot dogs" | inject echo "[!], [!]! Get your [!]!"

will output:

hot dogs, hot dogs! Get your hot dogs!

Sure, that's a silly example, but I've found it pretty handy. This is functionality I need a lot, but usually it requires a large amount of command substitution (which seems to be different in every shell), xargs magic, and other unix tricks.

Installation

Using the AUR

Run

yay inject-git

or an equivalent (such as yaourt) to install inject-git from the arch user repository.

Compile & Install manually

It's pretty simple! Just install Crystal, clone the repo, and run sudo make install.

sudo pacman -Syu crystal
git clone https://github.com/shinzlet/inject.git
cd inject
sudo make install

Usage

Inject has a very simple syntax. The basic form is:

inject [--shell /usr/bin/sh] [--delimiter [!]] [--text] [--block] command to be run here

Let's break that down quickly. You can specify the shell that inject will run your command in with the --shell (or -s) argument. By default, this is the bourne shell (sh).

You can also specify what delimiter/marker you want to use in your injection with --delimiter or -d. By default, inject replaces all instances of [!] in your command with whatever you piped into it.

If you don't want the command to be run at all, that's also fine! You can force inject to simply print the edited output to STDOUT with the --text or -t flag.

The block toggle specifies how inject handles multiline content. By default, inject runs on a per-line basis. This is convenient for running a single command multiple times with different arguments, for example. Specifying --block forces inject to treat the multiline text as a block, not splitting it at all.

Examples

This command will run in the fish shell.

echo "key" | inject --shell /usr/bin/fish "set -U [!] value"

This command will use the delimiter INSERT-HERE.

echo "now" | inject --delimiter INSERT-HERE "shutdown INSERT-HERE"

This command will simply perform a find-and-replace on the command string, then print it.

echo "like" | inject --text "I [!] fish."

This command will find-replace-print on the command string, but using a different delimiter.

echo "Susan" | inject -td <NAME> "Hi, <NAME>. I've always liked that name - <NAME>."

For the next two examples, I'll refer to the following files:

haiku.txt

I spent quite some time
Thinking of funny haikus
None of them panned out

keywords.txt

apple
orange
peach

This command uses block mode to treat a whole haiku as one text object.

cat haiku.txt | inject -b printf 'This is a beautiful haiku: "[!]"'

This command uses per-line execution (default behaviour), and a custom delimiter.

cat keywords.txt | inject -d @ "grep @ data.txt"

That's all the examples I've written thus far! I know these are pretty silly use cases, but I hope you can all find some more practical applications. I know that this little tool has already helped me out a couple times.