diff and patch

jimonitu

               
               
                diff 在两个文件间进行一行一行的比较，可以是任何的文本
如：diff test.c main.c
add parameter -u, it can man-readable
such as: diff -u test.c main.c
diff -c test.c main.c
diff options begin with -, so normally from-file and to-file may not begin with -. However, -- as an argument by itself treats the remaining arguments as file names even if they begin with -.  
Options
Below is a summary of all of the options that GNU diff accepts. Most options have two equivalent names, one of which is a single letter preceded by -, and the other of which is a long name preceded by --. Multiple single letter options (unless they take an argument) can be combined into a single command line word: -ac is equivalent to -a -c. Long named options can be abbreviated to any unique prefix of their name. Brackets ([ and ]) indicate that an option takes an optional argument.
-lines
    Show lines (an integer) lines of context. This option does not specify an output format by itself; it has no effect unless it is combined with -c or -u. This option is obsolete. For proper operation, patch typically needs at least two lines of context.
-a
    Treat all files as text and compare them line-by-line, even if they do not seem to be text.
-b
    Ignore changes in amount of white space.
-B
    Ignore changes that just insert or delete blank lines.
--brief
    Report only whether the files differ, not the details of the differences.
-c
    Use the context output format.
-C lines
--context[=lines]
    Use the context output format, showing lines (an integer) lines of context, or three if lines is not given. For proper operation, patch typically needs at least two lines of context.
--changed-group-format=format
    Use format to output a line group containing differing lines from both files in if-then-else format.
-d
    Change the algorithm to perhaps find a smaller set of changes. This makes diff slower (sometimes much slower).
-D name
    Make merged if-then-else format output, conditional on the preprocessor macro name.
-e
--ed
    Make output that is a valid ed script.
--exclude=pattern
    When comparing directories, ignore files and subdirectories whose basenames match pattern.
--exclude-from=file
    When comparing directories, ignore files and subdirectories whose basenames match any pattern contained in file.
--expand-tabs
    Expand tabs to spaces in the output, to preserve the alignment of tabs in the input files.
-f
    Make output that looks vaguely like an ed script but has changes in the order they appear in the file.
-F regexp
    In context and unified format, for each hunk of differences, show some of the last preceding line that matches regexp.
--forward-ed
    Make output that looks vaguely like an ed script but has changes in the order they appear in the file.
-h
    This option currently has no effect; it is present for Unix compatibility.
-H
    Use heuristics to speed handling of large files that have numerous scattered small changes.
--horizon-lines=lines
    Do not discard the last lines lines of the common prefix and the first lines lines of the common suffix.
-i
    Ignore changes in case; consider upper- and lower-case letters equivalent.
-I regexp
    Ignore changes that just insert or delete lines that match regexp.
--ifdef=name
    Make merged if-then-else format output, conditional on the preprocessor macro name.
--ignore-all-space
    Ignore white space when comparing lines.
--ignore-blank-lines
    Ignore changes that just insert or delete blank lines.
--ignore-case
    Ignore changes in case; consider upper- and lower-case to be the same.
--ignore-matching-lines=regexp
    Ignore changes that just insert or delete lines that match regexp.
--ignore-space-change
    Ignore changes in amount of white space.
--initial-tab
    Output a tab rather than a space before the text of a line in normal or context format. This causes the alignment of tabs in the line to look normal.
-l
    Pass the output through pr to paginate it.
-L label
--label=label
    Use label instead of the file name in the context format and unified format headers.
--left-column
    Print only the left column of two common lines in side by side format.
--line-format=format
    Use format to output all input lines in in-then-else format.
--minimal
    Change the algorithm to perhaps find a smaller set of changes. This makes diff slower (sometimes much slower).
-n
    Output RCS-format diffs; like -f except that each command specifies the number of lines affected.
-N
--new-file
    In directory comparison, if a file is found in only one directory, treat it as present but empty in the other directory.
--new-group-format=format
    Use format to output a group of lines taken from just the second file in if-then-else format.
--new-line-format=format
    Use format to output a line taken from just the second file in if-then-else format.
--old-group-format=format
    Use format to output a group of lines taken from just the first file in if-then-else format.
--old-line-format=format
    Use format to output a line taken from just the first file in if-then-else format.
-p
    Show which C function each change is in.
-P
    When comparing directories, if a file appears only in the second directory of the two, treat it as present but empty in the other.
--paginate
    Pass the output through pr to paginate it.
-q
    Report only whether the files differ, not the details of the differences.
-r
    When comparing directories, recursively compare any subdirectories found.
--rcs
    Output RCS-format diffs; like -f except that each command specifies the number of lines affected.
--recursive
    When comparing directories, recursively compare any subdirectories found.
--report-identical-files
-s
    Report when two files are the same.
-S file
    When comparing directories, start with the file file. This is used for resuming an aborted comparison.
--from-file=file
    Compare file to all operands. file can be a directory.
--to-file=file
    Compare all operands to file. file can be a directory.
--sdiff-merge-assist
    Print extra information to help sdiff. sdiff uses this option when it runs diff. This option is not intended for users to use directly.
--show-c-function
    Show which C function each change is in.
--show-function-line=regexp
    In context and unified format, for each hunk of differences, show some of the last preceding line that matches regexp.
--side-by-side
    Use the side by side output format.
--speed-large-files
    Use heuristics to speed handling of large files that have numerous scattered small changes.
--starting-file=file
    When comparing directories, start with the file file. This is used for resuming an aborted comparison.
--suppress-common-lines
    Do not print common lines in side by side format.
-t
    Expand tabs to spaces in the output, to preserve the alignment of tabs in the input files.
-T
    Output a tab rather than a space before the text of a line in normal or context format. This causes the alignment of tabs in the line to look normal.
--text
    Treat all files as text and compare them line-by-line, even if they do not appear to be text.
-u
    Use the unified output format.
--unchanged-group-format=format
    Use format to output a group of common lines taken from both files in if-then-else format.
--unchanged-line-format=format
    Use format to output a line common to both files in if-then-else format.
--unidirectional-new-file
    When comparing directories, if a file appears only in the second directory of the two, treat it as present but empty in the other.
-U lines
--unified[=lines]
    Use the unified output format, showing lines (an integer) lines of context, or three if lines is not given. For proper operation, patch typically needs at least two lines of context.
-v
--version
    Output the version number of diff.
-w
    Ignore white space when comparing lines.
-W columns
--width=columns
    Use an output width of columns in side by side format.
-x pattern
    When comparing directories, ignore files and subdirectories whose basenames match pattern.
-X file
    When comparing directories, ignore files and subdirectories whose basenames match any pattern contained in file.
-y
    Use the side by side output format.
   
diff3  
当两个人修改一个公用文件时diff3 就会发挥作用。它比较两个人做出的两套修改内容，创建第3个文件保存合并后的输出结果，并且指出双方修改的冲突之处。

patch把源代码补丁文件应用到你的源代码上，补丁文件记录了对代码的修改
such as:
diff test.c main.c >tes.patch
patch -p0 tes.patch

-pnum选项指定使用补丁前补丁中所鈌的文件名需要剥离的“/”的重数，例如，如果补丁中的文件是/home/kwall/src/sigrot/sigrot.1,则-p1的结果是home/kwall/src/sigrot/sigrot.1, -p4的结果是sigrot/sigrot.1,-p则剥去了除最终文件名之外的所有部分，得到sigrot.1
如果在安装完补丁后，发现错识误，只要简单地在原命令行中加上-R选项后再安装一次补丁就能得到 原来的文件


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