Read the Source Code of Shell Commands on Linux

To read the source code of shell commands on Linux, you can use the command line utility cat or less to view the file. You can also use a text editor such as vi, nano, or emacs to open and edit the code.

For example, to view the source code of the ls command, you can use the command −

cat /bin/ls

If you want to view the source code of a command that is installed from a package manager, you can use package manager command to find the location of the source code. For example, on a Debian-based system, you can use the command −

dpkg -L <package-name>

This will list the files included in the package, and you can then navigate to the appropriate file to view the source code.

You can also use the command find to locate the source code of command, for example −

find / -name ls 2>/dev/null

This will search your entire file system for a file named ls, and display its location.

Please note that Some commands may not have a source code, they are built in the shell or are binary files, in those cases you can use the command strings or objdump to see some of the code that the command is using.

Find the Source Code

To find the source code of a particular program, there are several methods you can try −

Check the official website of the program or project. Many open-source programs have their source code available for download on their official website.

Search for the program on GitHub, GitLab, or other code hosting platforms. Many open-source programs are hosted on these platforms, and you can easily find and download the source code.

Use package manager command, like apt-get source, yumdownloader, dnf download etc depends on the Linux distribution. These commands will download the source code of the package for you.

Check for the source code in the program's documentation. Some programs include links to their source code in their documentation.

Use a search engine to find the source code. You can search for the program's name followed by the keywords "source code" or "github" to find the source code.

It's worth noting that some software is closed-source, and the source code is not publicly available. In this case, you will not be able to find the source code.

Use the Package Manager

To use a package manager to find and download the source code of a program, you will first need to know the name of the package that the program is contained in. Once you know the package name, you can use the package manager command to download the source code.

Here are some examples of how to use a package manager to download the source code of a program on different Linux distributions −

On Debian-based systems (such as Ubuntu), you can use the command apt-get source <package-name> to download the source code of a package. For example, to download the source code of the ls command, you would use the command −

apt-get source coreutils

On Fedora, Red Hat and CentOS systems, you can use the command yumdownloader --source <package-name> to download the source code of a package. For example, to download the source code of the ls command, you would use the command −

yumdownloader --source coreutils

On Arch Linux-based systems, you can use the command pacman -S --needed base-devel to install the base development package, and then yaourt -S --aur <package-name> to download the source code of a package.

On OpenSuse systems, you can use the command zypper source-install <package-name> to download the source code of a package.

It's worth noting that some packages may not have the source code available, in that case you will get an error message.

Also it's good to note that before installing or building the source code, make sure you have the necessary dependencies and development tools installed on your system.

Debian-Based Systems

On Debian-based systems (such as Ubuntu, Mint, Debian, etc), you can use the apt-get command to download the source code of a package. The apt-get source command will download the source code of a package and all of its dependencies.

Here's an example of how to use the apt-get command to download the source code of the ls command on a Debian-based system −

apt-get source coreutils

This command will download the source code of the package coreutils which includes ls command, and all of its dependencies. The source code will be downloaded to the current working directory, and will be in the form of a .tar.gz file.

You can also use apt-get build-dep <package-name> to install the dependencies required to build the package.

You can then extract the source code using the command tar -xzvf <package-name>.tar.gz, and then navigate to the extracted directory to build and install the package using the command dpkg-buildpackage -us -uc

It's worth noting that apt-get source command will download the source code of the package in the version that is currently installed on your system. If you want to download a specific version of the package source code, you can use the -t option followed by the version number you want to download.

For example, to download version 8.31 of the coreutils package, you can use the command −

apt-get source -t 8.31-1 coreutils

Also, it's good to note that you need to have the apt-src package installed on your system to use the apt-get source command.

Red Hat-Based Systems

On Red Hat-based systems (such as Fedora, Red Hat Enterprise Linux, CentOS, etc), you can use the yumdownloader command to download the source code of a package.

Here's an example of how to use the yumdownloader command to download the source code of the ls command on a Red Hat-based system −

yumdownloader --source coreutils

This command will download the source code of the package coreutils, which includes the ls command, in the form of a .src.rpm file. The downloaded file will be located in the current working directory.

You can also use the yum-builddep command to install the dependencies required to build the package.

You can then use the rpmbuild command to extract the source code, and build the package.

rpmbuild --rebuild <package-name>.src.rpm

It's worth noting that yumdownloader command will download the source code of the package in the version that is currently installed on your system. If you want to download a specific version of the package source code, you can use the --releasever option followed by the version number you want to download.

For example, to download version 8.31 of the coreutils package, you can use the command −

yumdownloader --releasever=8.31 --source coreutils

Also, it's good to note that you need to have the yum-utils package installed on your system to use the yumdownloader command.

Conclusion

To find and download the source code of a program on Linux, you can use the package manager command that corresponds to your Linux distribution. On Debian-based systems, you can use the apt-get source command, and on Red Hat-based systems, you can use the yumdownloader --source command.