$ curl cheat.sh/
 cheat:diff 
# To view the differences between two files:
diff -u <file-1> <file-2>

# To view the differences between two directories:
diff -ur <dir-1> <dir-2>

# To ignore whitespace:
diff -ub <file-1> <file-2>

# To ignore blank lines:
diff -uB <file-1> <file-2>

# To ignore the differences between uppercase and lowercase:
diff -ui <file-1> <file-2>

# To report whether the files differ:
diff -q <file-1> <file-2>

# To report whether the files are identical:
diff -s <file-1> <file-2>

# To diff the output of two commands or scripts:
diff <(command1) <(command2)

# To generate a patch file from two files:
diff -Naur <file-1> <file-2> > <patch-file>

 tldr:diff 
# diff
# Compare files and directories.
# More information: <https://man7.org/linux/man-pages/man1/diff.1.html>.

# Compare files (lists changes to turn `old_file` into `new_file`):
diff old_file new_file

# Compare files, ignoring white spaces:
diff --ignore-all-space old_file new_file

# Compare files, showing the differences side by side:
diff --side-by-side old_file new_file

# Compare files, showing the differences in unified format (as used by `git diff`):
diff --unified old_file new_file

# Compare directories recursively (shows names for differing files/directories as well as changes made to files):
diff --recursive old_directory new_directory

# Compare directories, only showing the names of files that differ:
diff --recursive --brief old_directory new_directory

# Create a patch file for Git from the differences of two text files, treating nonexistent files as empty:
diff --text --unified --new-file old_file new_file > diff.patch

$
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