Demonstration of the difference between approaches https://superuser.com/a/663694/442895 and https://superuser.com/a/496421/442895 :
The test files were generated with:
$ </dev/random base64 | tr -s \\n \ | head -c 1000000 > file1.txt
For file2.txt I copied file1.txt and manually removed the 800th and the 80th characters.
$ diff -u <(tr -s \ \\n <file1.txt ) <(tr -s \ \\n <file2.txt)
--- /dev/fd/63 2024-06-03 04:21:07
+++ /dev/fd/62 2024-06-03 04:21:07
@@ -1,5 +1,5 @@
ZJ0LMAnZ8Iq2R1Y8gK347sSXc8xsOCPbDeliBd/v/ncwZN8XgxleqDK+JvpZXY3lCyDq1bey+4Z/
-5Mx8Nf3VzZFQnSHnXg+ZCXDO+roB/6NYsIomK0HE8u7yNij76rlSkPb+H7dnD4IxHhECBPsaH9V2
+5M8Nf3VzZFQnSHnXg+ZCXDO+roB/6NYsIomK0HE8u7yNij76rlSkPb+H7dnD4IxHhECBPsaH9V2
a/TXrK09x4mEFO4p1FP+k4wDB3aUTKlQ7re1E3AentxeC4tWs8nxzyAGQjIlwLDvGBxmfb/xaa5+
nHfXjMwMOdknGzeza3SFJqTtRISV1fGNWAfvil72bFSYnOeOHegBMxgzofaBt6ApVEi/38jNWFBY
5tvuCSwALVi/m4pkG8eAeXNWUNbuk+Xa9odv8Fs2X9ssQyM9DNhyEcDSD3GVXRwRfeZG8AlWvxSE
@@ -8,7 +8,7 @@
kcpQaW8dEWcfFl/C8TWDp21BW6LnAF62tI7Aj3ximOKDFWbkovvbmjymUAVTmEaZfPYO8YndsuM3
JUefUMjnsk1RQxE0GlcMQSe4Cf35bfFncHlA8rKvtC4jkPneFCZuteF+zH+WHwXgMZLFRMgUTNfQ
IwXXJBPC8tr47wNZOiU6OqigxMNYZZnxaTwp+wqPI5si15YgfGHyyRLSZGndQ4DNGUfc9LJB7W/j
-N9IVsMjcknx5w4nCSgXT4tx3s8FDAJOZ/puGVG7XJVWlRSTyody/cLqDpByGHwzKvfwEwhaoLubb
+N9IVsMjcknx5w4nCSgXT4tx3s8FDAOZ/puGVG7XJVWlRSTyody/cLqDpByGHwzKvfwEwhaoLubb
higduKjMNhVDtFWJtbPZwDxUha2a+GNKKbCU0nZvWGNws4pW5e14GLrjsbPHtVhzDZLfAxVckQ6F
JL+sGyLSFvnl0c5qaaVdGMj+K3CmnGqVSfxcH4i53xY+RwK6DJ3EGielmIEv3PjY40Ky99rLckQu
26Q6OjwStSBeETQ5panFlpu5lvyolZRK7l9dKl9VmpkMnynrb8IP6bsY/ErRLtmGOtsCkOlE7n3k$ diff -u <(./newline-every-50-chars.py file1.txt ) <(./newline-every-50-chars.py file2.txt)
--- /dev/fd/63 2024-06-03 04:22:16
+++ /dev/fd/62 2024-06-03 04:22:16
@@ -1,20000 +1,20000 @@
ZJ0LMAnZ8Iq2R1Y8gK347sSXc8xsOCPbDeliBd/v/ncwZN8Xgx
-leqDK+JvpZXY3lCyDq1bey+4Z/ 5Mx8Nf3VzZFQnSHnXg+ZCXD
-O+roB/6NYsIomK0HE8u7yNij76rlSkPb+H7dnD4IxHhECBPsaH
-9V2 a/TXrK09x4mEFO4p1FP+k4wDB3aUTKlQ7re1E3AentxeC4
-tWs8nxzyAGQjIlwLDvGBxmfb/xaa5+ nHfXjMwMOdknGzeza3S
-FJqTtRISV1fGNWAfvil72bFSYnOeOHegBMxgzofaBt6ApVEi/3
-8jNWFBY 5tvuCSwALVi/m4pkG8eAeXNWUNbuk+Xa9odv8Fs2X9
(39992 lines omitted--see attached file)It yields a very long diff.