diff command#

The diff command can compare the differences between two given files. If you use - as a file parameter, the content to be compared will come from the standard input. The diff command compares the differences between text files line by line. If the command specifies a directory comparison, it will compare files within that directory that have the same file names and will not compare any subdirectory files.

Syntax#

diff [-abBcdefHilnNpPqrstTuvwy][-<line>][-C <line>][-D <macro>][-I <string>][-S <file>][-W <width>][-x <file or folder>][-X <file>][--help][--left-column][--suppress-common-line][file or folder][file or folder]

Parameters#

• -a or --text: diff defaults to comparing text files line by line.
• -b or --ignore-space-change: Ignores changes in space characters.
• -B or --ignore-blank-lines: Ignores blank lines.
• -c: Displays all content and marks the differences.
• -C <line> or --context <line>: Same as executing the -c-<line> instruction.
• -d or --minimal: Uses a different algorithm to compare using smaller units.
• -D <macro> or ifdef <macro>: The output format of this parameter can be used for preprocessor macros.
• -e or --ed: The output format of this parameter can be used for an ed script file.
• -f or -forward-ed: The output format is similar to an ed script file, but displays the differences in the original file's order.
• -H or --speed-large-files: Speeds up the comparison of large files.
• -l<string> or --ignore-matching-lines<string>: If two files differ on certain lines and those lines also contain the characters or string specified in the option, the differences in those lines are not displayed.
• -i or --ignore-case: Ignores differences in case.
• -l or --paginate: Pages the result using the pr program.
• -n or --rcs: Displays the comparison result in RCS format.
• -N or --new-file: When comparing directories, if file A only appears in one directory, by default it will display Only in <folder>, if file A uses the -N option, diff will compare file A with a blank file.
• -p: When comparing C language program code files, it shows the name of the function where the difference occurs.
• -P or --unidirectional-new-file: Similar to -N, but only when the second directory contains files that the first directory doesn't, it will compare these files with a blank file.
• -q or --brief: Only displays whether there are differences, no detailed information is shown.
• -r or --recursive: Compares files in subdirectories.
• -s or --report-identical-files: If no differences are found, it still displays information.
• -S <file> or --starting-file <file>: When comparing directories, starts comparing from the specified file.
• -t or --expand-tabs: Expands tab characters in the output.
• -T or --initial-tab: Adds a tab character at the beginning of each line for alignment.
• -u, -U <columns> or --unified=<columns>: Displays the differences in the file content in a merged manner.
• -v or --version: Displays version information.
• -w or --ignore-all-space: Ignores all space characters.
• -W <width> or --width <width>: When using the -y parameter, specifies the column width.
• -x <file or folder> or --exclude <file or folder>: Excludes the specified files or directories from the comparison.
• -X<file> or --exclude-from<file>: You can save the file or directory types as a text file and then specify this text file in <file>.
• -y or --side-by-side: Displays the differences between files side by side.
• --help: Displays help.
• --left-column: When using the -y parameter, if a certain line in both files is the same, only the content of that line is displayed on the left side.
• --suppress-common-lines: When using the -y parameter, only the differences are displayed.

Examples#

Compare the differences between the file.txt and file2.txt files, and only output the differences.

diff file.txt file2.txt

Compare the differences between the file.txt and file2.txt files and display all content side by side. | indicates differences between the two files, < indicates one less line of content in the latter file compared to the former, > indicates one more line of content in the latter file compared to the former.

diff -y file.txt file2.txt

Compare the difference between file.txt and custom input. After entering the content, press Ctrl+D to output the EOF flag to end the input.

diff -y file.txt -

Daily Question#

Reference#