Diffstat recognizes the most popular types of output from diff:

unified

preferred by the patch utility.

context

best for readability, but not very compact.

default

not good for much, but simple to generate.

Diffstat detects the lines that are output by diff to tell which files are compared, and then counts the markers in the first column that denote the type of change (insertion, deletion or modification). These are shown in the histogram as "+", "-" and "!" characters.

If no filename is given on the command line, diffstat reads the differences from the standard input.

-c

prefix each line of output with "#", making it a comment-line for shell scripts.

-e file

redirect standard error to file.

-f format

specify the format of the histogram.

0

for concise, which shows only the value and a single histogram code for each of insert (+), delete (-) or modify (!)

1

for normal output,

2

to fill in the histogram with dots,

4

to print each value with the histogram.

Any nonzero value gives a histogram. The dots and individual values can be combined, e.g., -f6 gives both.

-h

prints the usage message and exits.

-k

suppress the merging of filenames in the report.

-l

lists only the filenames. No histogram is generated.

-n number

specify the minimum width used for filenames. If you don't specify this, diffstat uses the length of the longest filename, after stripping common prefixes.

-o file

redirect standard output to file.

-p number

override the logic that strips common pathnames, simulating the patch "-p" option.

-r code

provides optional rounding of the data shown in histogram, rather than truncating with error adjustments.

0

is the default. No rounding is performed, but accumulated errors are added to following columns.

1

rounds the data

2

rounds the data and adjusts the histogram to ensure that it displays something if there are any differences even if those would normally be rounded to zero.

-t

overrides the histogram, generates output of comma separated values.

-u

suppress the sorting of filenames in the report.

-v

show progress, e.g., if the output is redirected to a file, write progress messages to the standard error.

-V

prints the current version number and exits.

-w number

specify the maximum width of the histogram. The histogram will never be shorter than 10 columns, just in case the filenames get too large.

Diffstat runs in a portable UNIX® environment.

Diffstat is a single binary module, which uses no auxiliary files.

Diffstat makes a lot of assumptions about the format of a diff file.

There is no way to obtain a filename from the standard diff between two files with no options. Context diffs work, as well as unified diffs.

There's no easy way to determine the degree of overlap between the "before" and "after" displays of modified lines.

diff (1).

Thomas Dickey <dickey@invisible-island.net>.