One can easily compare the difference of files in two folders on the Command Line using diff command.
With folders we use rq as an argument and pass in the two folder names on the command line
diff -rq folder1 folder2
This will notify which corresponding files are different, and which files are unique in each folder. Once you know what files are different you then can run the diff file command on those files to see the actual difference.
With files one can pass below in to the command line with diff
diff file1.txt file2.txt
Commonly-Used diff Options
Here are some useful diff options to take note of:
| -b | Ignore any changes which only change the amount of whitespace (such as spaces or tabs). |
| -w | Ignore whitespace entirely. |
| -B | Ignore blank lines when calculating differences. |
| -y | Display output in two columns. |
These are only some of the most commonly-used diff options. What follows is a complete list of diff options and their function.
diff syntax
diff [OPTION]... FILES
Options
| –normal | output a “normal” diff. (This is the default) | ||||||
| -q, –brief | Produce output only when files differ. If there are no differences, output nothing. | ||||||
| -s, –report-identical-files | Report when two files are the same. | ||||||
| -c, -C NUM, –context[=NUM] | Provide NUM (default 3) lines of context. | ||||||
| -u, -U NUM, –unified[=NUM] | Provide NUM (default 3) lines of unified context. | ||||||
| -e, –ed | Output an ed script. | ||||||
| -n, –rcs | Output an RCS-format diff. | ||||||
| -y, –side by side | Format output in two columns. | ||||||
| -W, –width=NUM | Output at most NUM (default 130) print columns. | ||||||
| –left-column | Output only the left column of common lines. | ||||||
| –suppress-common-lines | Do not output lines common between the two files. | ||||||
| -p, –show-c-function | For files that contain C code, also show which C function each change is in. | ||||||
| -F,–show-function-line=RE | Show the most recent line matching regular expression RE. | ||||||
| –label LABEL | When displaying output, use the label LABEL instead of the file name. This option can be issued more than once for multiple labels. | ||||||
| -t, –expand-tabs | Expand tabs to spaces in output. | ||||||
| -T, –initial-tab | Make tabs line up by prepending a tab if necessary. | ||||||
| –tabsize=NUM | Define a tab stop as NUM (default 8) columns. | ||||||
| –suppress-blank-empty | Suppress spaces and/or tabs before empty output lines. | ||||||
| -l, –paginate | Pass output through pr to paginate it. | ||||||
| -r, –recursive | Recursively compare any subdirectories found. | ||||||
| -N, –new-file | If a specified file does not exist, perform the diff as if it is an empty file. | ||||||
| –unidirectional-new-file | Same as -n, but only applies to the first file. | ||||||
| –ignore-file-name-case | Ignore case when comparing file names. | ||||||
| –no-ignore-file-name-case | Consider case when comparing file names. | ||||||
| -x, –exclude=PAT | Exclude files that match filename pattern PAT. | ||||||
| -X, –exclude-from=FILE | Exclude files that match any filename pattern in file FILE. | ||||||
| -S, –starting-file=FILE | Start with file FILE when comparing directories. | ||||||
| –from-file=FILE1 | Compare FILE1 to all operands; FILE1 can be a directory. | ||||||
| –to-file=FILE2 | compare all operands to FILE2; FILE2 can be a directory. | ||||||
| -i, –ignore-case | ignore case differences in file contents. | ||||||
| -E, –ignore-tab-expansion | ignore changes due to tab expansion. | ||||||
| -b, –ignore-space-change | ignore changes in the amount of white space. | ||||||
| -w, –ignore-all-space | ignore all white space. | ||||||
| -B, –ignore-blank-lines | ignore changes whose lines are all blank. | ||||||
| -I, –ignore-matching-lines=RE | ignore changes whose lines all match regular expression RE. | ||||||
| -a, –text | treat all files as text. | ||||||
| –strip-trailing-cr | strip trailing carriage return on input. | ||||||
| -D, –ifdef=NAME | output merged file with “#ifdef NAME” diffs. | ||||||
| —GTYPE-group-format=GFMT | format GTYPE input groups with GFMT. | ||||||
| –line-format=LFMT | format all input lines with LFMT. | ||||||
| —LTYPE-line-format=LFMT | format LTYPE input lines with LFMT.
These format options provide fine-grained control over the output ofdiff, generalizing -D/–ifdef. LTYPE is old, new, or unchanged. GTYPE can be any of the LTYPE values, or the value changed. GFMT (but not LFMT) may contain:
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| %[–][WIDTH][.[PREC]]{doxX}LETTER | printf-style spec for LETTER |
LETTERs are as follows for new group, lower case for old group:
| F | first line number |
| L | last line number |
| N | number of lines = L – F + 1 |
| E | F – 1 |
| M | L + 1 |
| %(A=B?T:E) | if A equals B then T else E |
LFMT (only) may contain:
| %L | contents of line |
| %l | contents of line, excluding any trailing newline |
| %[–][WIDTH][.[PREC]]{doxX}n | printf-style spec for input line number |
Both GFMT and LFMT may contain:
| %% | A literal % |
| %c’C‘ | the single character C |
| %c’\OOO’ | the character with octal code OOO |
| C | the character C (other characters simply represent themselves) |
| -d, –minimal | try hard to find a smaller set of changes. |
| –horizon-lines=NUM | keep NUM lines of the common prefix and suffix. |
| –speed-large-files | assume large files and many scattered small changes. |
| –help | display a help message and exit. |
| -v, –version | output version information and exit. |
FILES takes the form “FILE1 FILE2” or “DIR1 DIR2” or “DIR FILE…” or “FILE… DIR“.
If the –from-file or –to-file options are given, there are no restrictions on FILE(s). If aFILE is a dash (“–“), diff reads from standard input.
Exit status is either 0 if inputs are the same, 1 if different, or 2 if diff encounters any trouble.
