# Cheatsheet & Examples: diff diff is a command-line utility used to compare the contents of two files and display the differences between them. It is commonly used to analyze changes in code, text, or configuration files. ## Compare Two Files Example Usage: `diff file1 file2` What it does: Compares the contents of `file1` and `file2` and outputs the lines that differ, indicating which lines are added, deleted, or changed. Command-line Arguments Explained: - `file1`: The first file to compare. - `file2`: The second file to compare. --- ## Generate a Unified Diff Example Usage: `diff -u file1 file2` What it does: Produces a "unified" diff format that shows the context around changed lines, making it easier to apply patches or understand the changes in code. Command-line Arguments Explained: - `-u`: Specifies the unified diff format, which includes a few lines of context before and after each change. --- ## Generate a Context Diff Example Usage: `diff -c file1 file2` What it does: Creates a "context diff" that includes more surrounding lines than the default format, useful for detailed analysis of changes in files. Command-line Arguments Explained: - `-c`: Produces a context diff, including lines before and after each difference. --- ## Compare Two Directories Recursively Example Usage: `diff -r dir1 dir2` What it does: Compares all files in `dir1` and `dir2`, including subdirectories, and reports on differences in file contents and structure. Command-line Arguments Explained: - `-r`: Recursively compares the contents of directories. --- ## Ignore Whitespace Differences Example Usage: `diff -w file1 file2` What it does: Compares files while ignoring changes in whitespace (spaces, tabs, line breaks), useful for focusing on actual content changes. Command-line Arguments Explained: - `-w`: Ignores all whitespace differences during the comparison. --- ## Compare Files Side by Side Example Usage: `diff -y file1 file2` What it does: Displays the contents of `file1` and `file2` side by side for easier visual comparison, especially for small files. Command-line Arguments Explained: - `-y`: Outputs the comparison in a side-by-side format. --- ## Ignore Case Sensitivity Example Usage: `diff -i file1 file2` What it does: Compares files in a case-insensitive manner, treating uppercase and lowercase letters as equivalent. Command-line Arguments Explained: - `-i`: Ignores case differences during the comparison. --- ## Show Only the Filenames with Differences Example Usage: `diff -q file1 file2` What it does: Prints a brief summary of whether the files differ, without showing the actual lines of difference. Command-line Arguments Explained: - `-q`: Quiet mode, only reports if files are different. --- ## Compare with a Specific Number of Context Lines Example Usage: `diff -C 3 file1 file2` What it does: Displays three lines of context around each difference, providing a balanced view of changes. Command-line Arguments Explained: - `-C 3`: Specifies three context lines to show for each difference. --- ## Compare Binary Files Example Usage: `diff -a file1 file2` What it does: Treats all files as text (even if they are binary), allowing comparison of their contents line by line. Command-line Arguments Explained: - `-a`: Treats each file as a text file, ensuring line-by-line comparison. --- ## Show Line Numbers for Differences Example Usage: `diff -n file1 file2` What it does: Outputs the line numbers where differences occur, aiding in locating changes. Command-line Arguments Explained: - `-n`: Displays line numbers for each change. --- ## Ignore Blank Lines in Comparison Example Usage: `diff -B file1 file2` What it does: Skips differences that involve only blank lines, making the output cleaner for files with formatting changes. Command-line Arguments Explained: - `-B`: Ignores blank lines when comparing files. --- ## Compare with a Custom Header Example Usage: `diff -L "Header1" -L "Header2" file1 file2` What it does: Adds custom headers to the output for clarity, especially when diffing files with different names or purposes. Command-line Arguments Explained: - `-L "Header1"`: Sets a custom header for `file1`. - `-L "Header2"`: Sets a custom header for `file2`. --- ## Compare Without Showing Exact Lines Example Usage: `diff -s file1 file2` What it does: Shows no output if the files are identical, and only reports if they differ. Command-line Arguments Explained: - `-s`: Suppresses output for identical files, making differences easier to spot. --- ## Compare with a Specific Line Separator Example Usage: `diff -t file1 file2` What it does: Replaces tabs with spaces or other characters for consistent formatting in the output. Command-line Arguments Explained: - `-t`: Expands tabs to spaces in the output for clarity. --- ## Compare with a Custom Output Format Example Usage: `diff -e file1 file2` What it does: Outputs the differences in ed command format, often used for creating patch files. Command-line Arguments Explained: - `-e`: Produces an ed script that can be used to transform `file1` into `file2`. --- ## Compare with Minimal Output Example Usage: `diff --brief file1 file2` What it does: Similar to `-q`, but provides a more concise output about file identity. Command-line Arguments Explained: - `--brief`: Outputs only whether the files are identical or different. --- ## Compare Files with a Specific Algorithm Example Usage: `diff -d file1 file2` What it does: Uses a different algorithm (e.g., for large or binary files) to find differences. Command-line Arguments Explained: - `-d`: Uses a different diff algorithm, which can be more efficient for certain file types.