Diff Directory Comparison Format
In the POSIX locale, each file that is present in only one directory will be reported using the following format:
"Only in %s: %s\n", <directory pathname>,
<filename>
In the POSIX locale, subdirectories that are common to the two directories may be reported with the following format:
"Common subdirectories: %s and %s\n", <directory1 pathname>,
<directory2 pathname>
For each file common to the two directories if the two files are not to be compared, the following format shall be used in the POSIX locale:
"File %s is a %s while file %s is a %s\n", <directory1 pathname>,
<file type of directory1 pathname>,
<directory2 pathname>,
<file type of directory2 pathname>
For each file common to the two directories, if the files are to be compared and are identical, no output shall be written. If the two files differ, the following format shall be written:
"diff %s %s %s\n", <diff_options>,
<filename1>,
<filename2>
where <diff_options> are the options as specified on the command line. Depending on these options, one of the following output formats will be used to write the differences.
All directory pathnames listed in this section will be relative to the original command line arguments. All other names of files listed in this section will be filenames (pathname components).
Diff Default Output Format
The default (without -e, -f, -c or -C options) diff utility output contains lines of these forms:
"%da%d\n", <num1>,
<num2>
"%da%d,%d\n", <num1>,
<num2>,
<num3>
"%dd%d\n", <num1>,
<num2>
"%d,%dd%d\n", <num1>,
<num2>,
<num3>
"%dc%d\n", <num1>,
<num2>
"%d,%dc%d\n", <num1>,
<num2>,
<num3>
"%dc%d,%d\n", <num1>,
<num2>,
<num3>
"%d,%dc%d,%d\n", <num1>,
<num2>,
<num3>,
<num4>
These lines resemble ed subcommands to convert file1 into file2. The line numbers before the action letters pertain to file1; those after pertain to file2. Thus, by exchanging a for d and reading the line in reverse order, one can also determine how to convert file2 into file1. As in ed, identical pairs (where num1 = num2) are abbreviated as a single number.
Following each of these lines, diff will write to standard output all lines affected in the first file using the format:
"<
%s", <line>
and all lines affected in the second file using the format:
">
%s", <line>
If there are lines affected in both file1 and file2 (as with the c subcommand), the changes are separated with a line consisting of three hyphens:
"---\n"
Diff -e Output Format
With the -e option, a script will be produced that will, when provided as input to ed, along with an appended w (write) command, convert file1 into file2. Only the a (append), c (change), d (delete), i (insert), and s (substitute) commands of ed will be used in this script. Text lines, except those consisting of the single character period (.), will be output as they appear in the file.Diff -f Output Format
With the -f option, an alternative format of script will be produced. It will be similar to that produced by -e, with the following differences:-
It will be expressed in reverse sequence;
the output of
-e
will order changes from the end of the file to the beginning;
the
-f
from beginning to end.
-
The command form
<lines>
<command-letter>
used by
-e
will be reversed.
For example,
10c
with
-e
would be
c10
with
-f.
-
The form used for ranges of line numbers will be
space-character-separated,
rather than comma-separated.
Diff -c or -C Output Format
With the -c or -C option, the output format will consist of affected lines along with surrounding lines of context. The affected lines will show which ones need to be deleted or changed in file1, and those added from file2. With the -c option, three lines of context, if available, will be written before and after the affected lines. With the -C option, the user can specify how many lines of context will be written. The exact format follows.The name and last modification time of each file will be output in the following format:
and a string of 15 asterisks:
"*** %s %s\n", file1,
<file1 time stamp>
"--- %s %s\n", file2,
<file2 time stamp>
"***************\n"
Each <file> field will be the pathname of the corresponding file being compared. The pathname written for standard input is unspecified.
In the POSIX locale, each <timestamp> field will be equivalent to the output from the following command:
date "+%a %b %e %T %Y"
without the trailing
newline character,
executed at the time of last modification
of the corresponding file
(or the current time, if the file is standard input).
Then, the following output formats will be applied for every set of changes.
First, the range of lines in file1 will be written in the following format:
"*** %d,%d ****\n", <beginning line number>,
<ending line number>
Next, the affected lines along with lines of context (unaffected lines) will be written. Unaffected lines will be written in the following format:
"
%s", <unaffected_line>
Deleted lines will be written as:
"-
2%s", <deleted_line>
Changed lines will be written as:
"!
%s", <changed_line>
Next, the range of lines in file2 will be written in the following format:
"--- %d,%d ----\n", <beginning line number>,
<ending line number>
Then, lines of context and changed lines will be written as described in the previous formats. Lines added from file2 will be written in the following format:
"+
%s", <added_line>