sdiff

sdiff [-o output] [-w width] [-sbBiW] [options] file1 file2

sdiff compares two files side by side. It displays corresponding lines in parallel columns, marking differences with symbols.Output symbols indicate relationship: blank (identical), | (different), < (only in left), > (only in right). This visual format makes differences immediately apparent.Interactive merge mode (-o) creates a combined file from the two inputs. At each difference, you choose: left (l), right (r), edit left (el), edit right (er), or both (b). This enables manual resolution of differences.Width setting (-w) controls output columns. Narrow widths truncate lines; wider widths show more content. Terminal width is commonly used (e.g., -w 80 or -w $COLUMNS).Suppressing common lines (-s) shows only differences, useful for focusing on changes in files that are mostly identical.Whitespace and case options help compare files with formatting differences that aren't substantive.

-o FILE, --output FILE

Interactive merge to output file.

Output width in columns.

Don't show identical lines.

Show only left column for common lines.

Ignore changes in whitespace amount.

Ignore blank line changes.

Case-insensitive comparison.

Ignore all whitespace.

Expand tabs to spaces.

Strip trailing carriage returns.

Treat all files as text.

Find minimal set of changes.

Heuristics for large files.

Binary files display poorly. Very long lines may be truncated. Interactive mode requires terminal. Wide files need wide terminal or scrolling. Not as feature-rich as diff for scripting.

sdiff is part of GNU diffutils, developed by the Free Software Foundation. Side-by-side diff originated in Unix research, providing visual comparison before graphical diff tools existed. The GNU version added interactive merge mode and various comparison options.

diff(1), diff3(1), cmp(1), vimdiff(1)