Use ctags and cscope to read source code online: Tutorial of TheLinuxCrossReferencer

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When there is an Internet connection, it is a great pleasure to use LXR (TheLinuxCrossReferencer) to read the source code online. In the absence of network linux kernel code reading toolubuntu linux, it becomes a bit reluctant to search the kernel source code only through vim. Next, this article will introduce a tool to quickly locate source code: ctags and cscope. Through the vim editor Linux standard tutorial and the above two tools, you can quickly locate the source code you want to view. Okay, let’s get started!

1. Download the latest kernel source code package and extract it to the main directory

The next steps can actually be performed in the current system kernel source code directory, but for the sake of insurance, it is best to create a special directory to store the source code in the home directory. The source code directories mentioned below all refer to the source code directories under the home directory.

2. Install ctags

Use command: sudoapt-getinstallctags

3.Install cscope

Use command: sudoapt-getinstallcscope

4. Into tag file

Generate tag files in the source code directory through the command maketags (you can also use: ctags-R)

5. Generate index file

Run the makecscope command in the source directory (you can also use: cscope-indexer-r) to generate an index file.

6. Export the index file into vim

Use the command to open the vim configuration file: sudogedit/etc/vim/vimrc; then add the following code under the file:

iffilereadable("cscope.out")

csaddcscope.out

endif

This way you can use cscope directly every time you open vim.

After completing the above steps, you can quickly locate the source code through vim. The ctags and cscope installed above are both source code indexing tools, so it is okay to install only one of the three. Yes, although ctags can quickly locate the entered tag, cscope is more flexible in its use. Therefore, it is more convenient to install and use both at the same time. Below are some simple usage methods for reference only.

1.Use ctags

The use of ctags is very simple. First, enter the source code directory, open the vim editor, enter: tagtag_name in command mode and press Enter. Generally, tag_name can be a structure name, a function name, a macro variable name, etc. Generally, after entering the above command, since the found tags are not unique, you need to use the following commands together:

tfirst: jump to the first

tnext: jump to next

tlast: jump to the last

2. Use cscope

Although ctags is convenient and fast to use, sometimes it is more flexible to use cscopeLinux kernel code reading tool, first you can look at the help file of cscope:

Quote

cscope command:

add: Add a new database (usage: addfile|dir[pre-path][flags])

find: Query a pattern (usage: findc|d|e|f|g|i|s|tname)

c: Find the function that calls this function

d: Find the function called by this function

e: Find this egrep pattern

f: Found this folder

g: Find this definition

i: Find file #include this file

s: Find this C symbol

t: Find its formal parameter

help: display this information (usage: help)

kill: end a connection (usage: kill#)

reset: reset all connections (usage: reset)

show: display connection (usage: show)

Through the previous help file, you can find that if you want to find the definition code of the request_irq function, you can use this command: csfindgrequest_irq to search. In most cases, the search results are not unique because you need to continue viewing through header files in multiple results.

Generally, the header file is roughly located through cscope, and then detailedly located in the header file through ctags. Although these two tools are not limited to the above usage, more usages can be gradually explored through in-depth use, and the effect will be better when combined with regular expressions.

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