Add Diff Two Files In Unified Format as a Unix TIL

README.md

@@ -10,7 +10,7 @@ working across different projects via [VisualMode](https://www.visualmode.dev/).
 
 For a steady stream of TILs, [sign up for my newsletter](https://visualmode.kit.com/newsletter).
 
-_1723 TILs and counting..._
+_1724 TILs and counting..._
 
 See some of the other learning resources I work on:
 
@@ -1641,6 +1641,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Curling For Headers](unix/curling-for-headers.md)
 - [Curling With Basic Auth Credentials](unix/curling-with-basic-auth-credentials.md)
 - [Determine ipv4 And ipv6 Public IP Addresses](unix/determine-ipv4-and-ipv6-public-ip-addresses.md)
+- [Diff Two Files In Unified Format](unix/diff-two-files-in-unified-format.md)
 - [Different Ways To Generate A v4 UUID](unix/different-ways-to-generate-a-v4-uuid.md)
 - [Display All The Terminal Colors](unix/display-all-the-terminal-colors.md)
 - [Display Free Disk Space](unix/display-free-disk-space.md)

unix/diff-two-files-in-unified-format.md

@@ -0,0 +1,78 @@
+# Diff Two Files In Unified Format
+
+The `diff` command is a standalone utility that can be used to get the
+difference between two files. It is similar to what you might expect when
+running `git diff` which compares two different versions of the same file. The
+`diff` command predates `git` and its unified format is what became the standard
+that `git` uses for its own diff implementation.
+
+Running `diff` with two files as is gives output like the following:
+
+```bash
+❯ diff startup.sh startup2.sh
+10,13c10,14
+< declare -A SESSIONS=(
+<   ["TIL"]="$HOME/dev/jbranchaud/til:setup_til"
+<   ["PLP"]="$HOME/dev/jbranchaud/pool-league-pro:"
+<   ["client-app"]="$HOME/dev/client/client-app:"
+---
+> # Sessions will be created in the order listed here
+> SESSIONS=(
+>   "TIL:$HOME/dev/jbranchaud/til:setup_til"
+>   "PLP:$HOME/dev/jbranchaud/pool-league-pro:"
+>   "client-app:$HOME/dev/client/client-app:"
+73,74c74,75
+<   for session_name in TIL PLP client-app; do
+<     IFS=':' read -r directory setup_function <<<"${SESSIONS[$session_name]}"
+---
+>   for session_config in "${SESSIONS[@]}"; do
+>     IFS=':' read -r session_name directory setup_function <<<"$session_config"
+```
+
+That's readable at a glance, but the unified format (with the `-u` flag) can
+provide more context:
+
+```bash
+❯ diff -u startup.sh startup2.sh
+--- startup.sh  2026-01-10 12:46:52
++++ startup2.sh 2026-01-10 12:48:00
+@@ -7,10 +7,11 @@
+
+ # Session configurations
+ # Format: "session_name:directory:setup_function"
+-declare -A SESSIONS=(
+-  ["TIL"]="$HOME/dev/jbranchaud/til:setup_til"
+-  ["PLP"]="$HOME/dev/jbranchaud/pool-league-pro:"
+-  ["client-app"]="$HOME/dev/client/client-app:"
++# Sessions will be created in the order listed here
++SESSIONS=(
++  "TIL:$HOME/dev/jbranchaud/til:setup_til"
++  "PLP:$HOME/dev/jbranchaud/pool-league-pro:"
++  "client-app:$HOME/dev/client/client-app:"
+ )
+
+ # Setup function for TIL session
+@@ -70,8 +71,8 @@
+   echo ""
+
+   # Create sessions in order
+-  for session_name in TIL PLP client-app; do
+-    IFS=':' read -r directory setup_function <<<"${SESSIONS[$session_name]}"
++  for session_config in "${SESSIONS[@]}"; do
++    IFS=':' read -r session_name directory setup_function <<<"$session_config"
+     create_session "$session_name" "$directory" "$setup_function"
+   done
+```
+
+Here we get additional context like surrounding lines and file name details.
+
+While this is useful on its own, it also has the added benefit of making the
+output compatible with other tools we may already be using. For instance, I'm
+already using [delta](https://github.com/dandavison/delta) as my [git pager](https://github.com/jbranchaud/dotfiles/blob/main/gitconfig#L51) and [git differ](https://github.com/jbranchaud/dotfiles/blob/main/gitconfig#L139).
+
+With the unified format, I can pipe the output directly to `delta` to get a
+better view of the diff that is colorized and includes syntax highlighting.
+
+```bash
+❯ diff -u startup.sh startup2.sh | delta
+```