new post: read-content-into-file-vim

content/posts/read-content-into-file-vim/index.md

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+---
+title: "Read Content Into a File with Vim"
+date: 2024-12-10 21:42:17-06:00
+# lastmod: 2024-12-07
+draft: false
+description: "Using Vim's :r[ead] command to import content from another file or insert command output without leaving the editor."
+featured: false
+toc: true
+reply: true
+categories: Tips # Backstage, ChromeOS, Code, Self-Hosting, VMware
+tags:
+  - linux
+  - shell
+---
+
+I've been comfortable working with Vim for what feels like ages, but I still regularly learn about features and capabilities I'd overlooked.
+
+I recently discovered [Vim's `:r[ead]` command](https://vimhelp.org/insert.txt.html#%3Aread) which makes it easy to insert data from another file. I put this to use when I was configuring Netplan on a Linux VM while connected through a remote console session (without copy/paste support) and needed to include an interface's MAC address. Through the magic of Vim, I was able to pull that data straight into the file. For example:
+
+```yaml
+network:
+  ethernets:
+    ens18:
+      [...]
+      match:
+        macaddress: # and then I entered...
+`<Esc>:r /sys/class/net/ens18/address<CR>`
+```
+
+I hit `<Esc>` to switch to normal mode, invoked the `:r[ead]` command, and pointed it to the `/sys` file which holds the MAC address for the interface. The address was then inserted straight into the file:
+
+```yaml
+network:
+  ethernets:
+    ens18:
+      [...]
+      match:
+        macaddress:
+de:ad:be:ef:ca:fe # [tl! ~~]
+```
+
+`:r[ead]` inserts the extracted content on the line *after* the cursor so I just needed to quickly back it up to the `macaddress` line but that was still a pretty easy exercise.
+
+```yaml
+network:
+  ethernets:
+    ens18:
+      [...]
+      match:
+        macaddress: de:ad:be:ef:ca:fe # [tl! ~~]
+```
+
+This approach also works well for capturing output from a command with `:r !command`, such as generating a random password for a Docker Compose stack:
+
+```yaml
+services:
+  my_app:
+    [...]
+    environment:
+      DB_SECRET:
+`<Esc>:r !apg -M NCL -m 32 -a 1 -n 1`
+```
+
+would yield something like:
+
+
+```yaml
+services:
+  my_app:
+    [...]
+    environment:
+      DB_SECRET:
+Cn6kp5y2BBk0VvAisULO4dxkXaGyFJ4f # [tl! ~~]
+```
+
+And again just a quick bit of rearranging...
+
+
+```yaml
+services:
+  my_app:
+    [...]
+    environment:
+      DB_SECRET: Cn6kp5y2BBk0VvAisULO4dxkXaGyFJ4f # [tl! ~~]
+```
+
+Being able to merge in data from elsewhere without leaving the editor is a pretty slick trick, don't you think?
+