How to Use the Command `diffstat` (with Examples)

The diffstat command is a utility that creates a histogram or a summary table from the output produced by the diff command. The diff command is used to compare files or directories, allowing users to see differences such as lines added, removed, or changed. However, the results can sometimes be overwhelming, especially when dealing with large files or multiple changes. diffstat helps by offering a condensed summary of these differences, thereby providing an easier way to understand the scope of changes.

Use Case 1: Display Changes in a Histogram

Code:

diff path/to/file1 path/to/file2 | diffstat

Motivation for Using the Example:

When working on large projects, developers often need to review changes between code iterations. Reading through extensive line-by-line differences can be time-consuming. By visualizing the differences in a histogram, developers can quickly gauge the scale of modifications and focus on the most affected areas. This becomes particularly useful during code reviews, where a visual representation can speed up the assessment process.

Explanation for Every Argument and Command:

• diff: This is the actual command that compares files or directories. It identifies lines that have been added, removed, or altered.
• path/to/file1: The path to the first file being compared.
• path/to/file2: The path to the second file being compared.
• |: This pipe symbol takes the output from the diff command and provides it as input to the diffstat command.
• diffstat: This command reads the output from diff and produces a histogram, displaying the number of lines inserted, deleted, or modified.

Example Output:

 file1.c |   13 +++++++++++--
 file2.c |    5 ++---
 file3.c |    8 ++++----

The display shows each file with the number of lines added (+), removed (-), and a brief visual summary of changes using symbols.

Use Case 2: Display Inserted, Deleted, and Modified Changes as a Table

Code:

diff path/to/file1 path/to/file2 | diffstat -t

Motivation for Using the Example:

Software developers often need to report on changes made in a series of files or a project as a whole. A table format can help in gathering statistics of these changes, providing an overview of the insertions, deletions, and modifications in a structured manner. This formatted view is especially useful in reports where changes need to be documented clearly and concisely.

Explanation for Every Argument and Command:

• diff: As before, this command identifies the differences between two files.
• path/to/file1: The path to the first file being compared.
• path/to/file2: The path to the second file being compared.
• |: The pipe connects the output of diff to the input of diffstat.
• diffstat: Processes the diff output.
• -t: This option modifies the output of diffstat to display changes in a tabular format, detailing inserted, deleted, and modified lines in numerical form.

Example Output:

 file     |  inserted  |  deleted  |  modified 
----------------------------------------------
 file1.c  |    10      |    3      |    2      
 file2.c  |    3       |    4      |    1      
 file3.c  |    8       |    5      |    3      
----------------------------------------------
 total    |    21      |   12      |    6

In this table, each file’s changes are itemized, allowing users to clearly see the scope of each type of change—insertions, deletions, and modifications—in an easily understandable format.

Conclusion

The diffstat command enhances the ability to interpret changes between file versions by providing succinct visual or tabular summaries of differences. By using its different options, users can customize their view, encourage more efficient reviews, and produce clearer reports of changes. This makes it an incredibly valuable tool for developers and any professional dealing with file comparisons in their workflow.