How to view linux Command source code

For details about how to view the linux Command source code-Linux general technology-Linux technology and application information, see the following. I 've been using linux for a while. Sometimes I want to see the source code of ls, cat, more, and other commands. I haven't found the source code in the downloaded kernel source code. I searched online and summarized the method as follows:

Take the ls command source code as an example. First, search for the package where the command is located. The command is as follows:
Lpj @ lpj-linux :~ $ Which ls
/Bin/ls

Use the command to search for the package of the software. The Code is as follows:
Lpj @ lpj-linux :~ $ Dpkg-S/bin/ls
Coreutils:/bin/ls

From the previous step, we can know the implementation of the ls command in the package coreutils, and install it with apt (indicating that the installation is ambiguous, mainly to distinguish apt-get-d) and decompress the source code of the package, the Code is as follows:
Sudo apt-get source coreutils
#### Cd/usr/src/coreutils-XXX # XXX indicates the version number
Cd.
Sudo tar zxvf coreutils-XXX.tar.gz

Or download the source code, manually patch it, and decompress it. The Code is as follows:
Sudo apt-get-d source coreutils
Cd/usr/src
Tar zxvf coreutils-XXX.tar.gz
Gzip-d coreutils-XXX.diff.gz # This step will generate a coreutils-XXX.diff File
Patch-p0 <coreutils-XXX.diff
Cd coreutils-XXX

OK. After these steps are completed, you can view the source code of each command in/usr/src/coreutils-XXX/src.

Reference: http://zhan.renren.com/ilinux