|Comparing and Merging Files with GNU diff and patch|
by David MacKenzie, Paul Eggert, and Richard Stallman
Paperback (6"x9"), 120 pages
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2.6.2 Line Formats
Line formats control how each line taken from an input file is output as part of a line group in if-then-else format.
For example, the following command outputs text with a one-character change indicator to the left of the text. The first character of output is ‘-’ for deleted lines, ‘|’ for added lines, and a space for unchanged lines. The formats contain newline characters where newlines are desired on output.
diff \ --old-line-format='-%l ' \ --new-line-format='|%l ' \ --unchanged-line-format=' %l ' \ old new
To specify a line format, use one of the following options. You should quote format, since it often contains shell metacharacters.
- formats lines just from the first file.
- formats lines just from the second file.
- formats lines common to both files.
- formats all lines; in effect, it sets all three above options simultaneously.
In a line format, ordinary characters represent themselves; conversion specifications start with ‘%’ and have one of the following forms.
- stands for the contents of the line, not counting its trailing newline (if any). This format ignores whether the line is incomplete; See section 3 Incomplete Lines.
- stands for the contents of the line, including its trailing newline (if any). If a line is incomplete, this format preserves its incompleteness.
- stands for ‘%’.
- where C is a single character, stands for C. C may not be a backslash or an apostrophe. For example, ‘%c':'’ stands for a colon.
- where O is a string of 1, 2, or 3 octal digits, stands for the character with octal code O. For example, ‘%c'\0'’ stands for a null character.
where F is a
printfconversion specification, stands for the line number formatted with F. For example, ‘%.5dn’ prints the line number using the
"%.5d". See section 2.6.1 Line Group Formats, for more about printf conversion specifications.
The default line format is ‘%l’ followed by a newline character.
If the input contains tab characters and it is important that they line
up on output, you should ensure that ‘%l’ or ‘%L’ in a line
format is just after a tab stop (e.g. by preceding ‘%l’ or
‘%L’ with a tab character), or you should use the
Taken together, the line and line group formats let you specify many
different formats. For example, the following command uses a format
similar to normal
diff format. You can tailor this command
to get fine control over
diff \ --old-line-format='< %l ' \ --new-line-format='> %l ' \ --old-group-format='%df%(f=l?:,%dl)d%dE %<' \ --new-group-format='%dea%dF%(F=L?:,%dL) %>' \ --changed-group-format='%df%(f=l?:,%dl)c%dF%(F=L?:,%dL) %<--- %>' \ --unchanged-group-format=" \ old new
|ISBN 0954161750||Comparing and Merging Files with GNU diff and patch||See the print edition|