Introduction to Patch application and production methods in Linux

The application and production method of Patch in Linux is introduced because during the u-boot porting process, there are several common files to be modified. It is too troublesome to manually modify each time. Patch creation can solve this problem. The collection of learning materials is relatively simple. The method 1 is similar to this kind of elementary problem. There are a lot of online materials. google or baidu searches for valuable materials and then selects valuable materials. The method 2 is to read man's online documents. To complete the collection, of course, we will eventually conduct an experiment on our own Linux system, make a summary, and digest and absorb your own things. To remove such a wrong idea, you must learn it all. You need to know that it is impossible to learn all at once. You can only learn the most common ones first. In the future, you will gradually enrich your learning experience and eventually reach a relatively high level. The principle is to apply what you have learned on a daily basis to promote learning. First, describe diff and patch. All options in the man online document will not be described here, which is unnecessary. In the 99% period, we only use a few options. Therefore, you must learn these options. 1. diff NAME diff-find differences between two files SYNOPSIS diff [options] from-file to-file. In short, diff is used to compare the differences between two files, then record it, the so-called diff patch. Syntax format: diff [Option] source file (folder) Destination File (folder), that is, to patch the source file (folder) to make it into the destination file (folder ), the term is "Upgrade ". The following describes the three most common options:-r is a recursive option. With this option set, diff compares all the corresponding files in the source code directories of two different versions, including sub-directory files. -N option ensures that the patch file correctly processes the files that have been created or deleted. -U option creates patch files in a uniform format, which is more compact than the default format. 2. patch NAME patch-apply a diff file to an original SYNOPSIS patch [options] [originalfile [patchfile] but usually just patch-pnum in short, patch is a patch created by diff to convert the source file (folder) and target file (folder. This means you can have the source file (folder)> the target file (folder) or the target file (folder)> The source file (folder ). The following describes some of the most common options:-p0 option to find the target file (folder)-p1 option from the current directory to ignore the first-level directory and start searching from the current directory. Here is an example: --- old/modules/pcitable Mon Sep 27 11:03:56 1999 + + new/modules/pcitable Tue Dec 19 20:05:41 2000 if the parameter-p0 is used, it indicates finding a folder named old from the current directory and searching for the pcitable file under modules under it to perform the patch operation. If the-p1 parameter is used, ignore the first-level directory (regardless of the old directory), find the modules folder from the current directory, and find pcitable under it. The premise is that the current directory must be the directory where modules is located. The diff patch file can be located anywhere, as long as the path of the diff patch file is specified. Of course, you can use relative paths or absolute paths. However, I usually use relative paths. -E Option indicates that if an empty file is found, delete it. The-R option indicates that the "new" file and "old" file in the patch file are to be replaced now (in fact, the new version is patched to make it an old version) the following examples are used to analyze and solve the problem. There are two types: patching a single file and patching multiple files in the folder. Environment: log on with an armlinux user under RedHat 9.0. The directory tree is as follows: | -- bootloader | -- debug | -- images | -- kernel | -- program | -- rootfiles | -- software | -- source | -- sysapps | -- tmp '-- create a patch under the program folder under tools folder is used as an experiment, then go to the patch folder. 1. patch a single file 1. Create test files test0 and test1 [armlinux @ lqm patch] $ cat> test0 <> 111111> 111111> EOF [armlinux @ lqm patch] $ more test0 111111 111111 111111 [armlinux @ lqm patch] $ cat> test1 <> 222222> 111111> 222222> EOF [armlinux @ lqm patch] $ more test1 111111 111111 222222 111111 2. Use diff to create a patch test1.patch [armlinux @ lqm patch] $ diff-uN test0 test1> test1.patch [Note: the-r option is not required because of a single file. There is no relation between the option sequence, that is, it can be-uN or-Nu .] [Armlinux @ lqm patch] $ ls test0 test1 test1.patch [armlinux @ lqm patch] $ more test1.patch patch file structure patch header is two lines starting with ---/++, indicates the file to be patched. --- The beginning indicates the old file, and the beginning of ++ indicates the new file. One patch file contains multiple patches. One patch file may contain many sections starting with ---/++. Each section is used for a patch. Therefore, a patch file can contain many patches. A block is the part to be modified in the patch. It usually starts and ends with something that does not need to be modified. They are only used to indicate the location to be modified. They usually start with @ and end with another block or a new patch header. The indention block of the block is reduced into a column, which indicates whether to add or delete the row. The first column + number of the block indicates that this row is to be added. -Indicates that this row is to be deleted. There is no plus sign or minus sign, indicating that this is just referenced and does not need to be modified. **************************************** * ********************** The diff Command records the first creation time of the two files in the patch file, *** --- test0 09:12:01. 000000000 + 0800 ++ test1 09:13:09. 000000000 + 0800 @-222222 + 111111 @ + 111111 222222-111111 + [armlinux @ lqm patch] $ patch-p0 <test1.patch patching file test0 [armlinux @ lqm patch] $ ls test0 test1 test1.patch [armlinux @ lqm patch] $ cat test0 222222 111111 222222 111111 3. patches can be removed, recover the old version [armlinux @ lqm patch] $ patch-RE-p0 <test1.patch patching file test0 [armlinux @ lqm patch] $ ls test0 test1 test1.patch [armlinux @ lqm patch] $ cat test0 111111 111111 111111