diff(1) - compare files line by line
       output a normal diff (the default)
-q, --brief
       report only when files differ
-s, --report-identical-files
       report when two files are the same
-c, -C NUM, --context[=NUM]
       output NUM (default 3) lines of copied context
-u, -U NUM, --unified[=NUM]
       output NUM (default 3) lines of unified context
-e, --ed
       output an ed script
-n, --rcs
       output an RCS format diff
-y, --side-by-side
       output in two columns
-W, --width=NUM
       output at most NUM (default 130) print columns
       output only the left column of common lines
       do not output common lines
-p, --show-c-function
       show which C function each change is in
-F, --show-function-line=RE
       show the most recent line matching RE
--label LABEL
       use LABEL instead of file name (can be repeated)
-t, --expand-tabs
       expand tabs to spaces in output
-T, --initial-tab
       make tabs line up by prepending a tab
       tab stops every NUM (default 8) print columns
       suppress space or tab before empty output lines
-l, --paginate
       pass output through `pr' to paginate it
-r, --recursive
       recursively compare any subdirectories found
-N, --new-file
       treat absent files as empty
       treat absent first files as empty
       ignore case when comparing file names
       consider case when comparing file names
-x, --exclude=PAT
       exclude files that match PAT
-X, --exclude-from=FILE
       exclude files that match any pattern in FILE
-S, --starting-file=FILE
       start with FILE when comparing directories
       compare FILE1 to all operands; FILE1 can be a directory
       compare all operands to FILE2; FILE2 can be a directory
-i, --ignore-case
       ignore case differences in file contents
-E, --ignore-tab-expansion
       ignore changes due to tab expansion
-b, --ignore-space-change
       ignore changes in the amount of white space
-w, --ignore-all-space
       ignore all white space
-B, --ignore-blank-lines
       ignore changes whose lines are all blank
-I, --ignore-matching-lines=RE
       ignore changes whose lines all match RE
-a, --text
       treat all files as text
       strip trailing carriage return on input
-D, --ifdef=NAME
       output merged file with `#ifdef NAME' diffs
       format GTYPE input groups with GFMT
       format all input lines with LFMT
       format LTYPE input lines with LFMT

       These format options provide fine-grained control over the output

              of diff, generalizing -D/--ifdef.

       LTYPE is `old', `new', or `unchanged'.
              GTYPE is LTYPE or `changed'.

              GFMT (only) may contain:

       %<     lines from FILE1

       %>     lines from FILE2

       %=     lines common to FILE1 and FILE2

              printf-style spec for LETTER

              LETTERs are as follows for new group, lower case for old group:

       F      first line number

       L      last line number

       N      number of lines = L-F+1

       E      F-1

       M      L+1

              if A equals B then T else E

              LFMT (only) may contain:

       %L     contents of line

       %l     contents of line, excluding any trailing newline

              printf-style spec for input line number

              Both GFMT and LFMT may contain:

       %%     %

       %c'C'  the single character C

              the character with octal code OOO

       C      the character C (other characters represent themselves)
-d, --minimal
       try hard to find a smaller set of changes
       keep NUM lines of the common prefix and suffix
       assume large files and many scattered small changes
--help display this help and exit
-v, --version
       output version information and exit
FILES are `FILE1 FILE2' or `DIR1 DIR2' or `DIR FILE...' or `FILE... DIR'.  If --from-file or --to-file is
given, there are no restrictions on FILE(s).  If a FILE is `-', read standard input.  Exit status is 0 if
inputs are the same, 1 if different, 2 if trouble.