Use the sd Command for Find and Replace on Linux

sd is a command-line tool for finding and replacing text, similar to sed. But, unlike sed, sd focuses on substitution only, allowing it to use simpler and easier to read commands. sd also uses a common regex syntax, giving you more familiar, well-documented, and powerful search options.

In this guide you learn more about sd and how it compares to sed. You also learn how to install sd and get started using it on your Linux system.

Before You Begin

1. If you have not already done so, create a Linode account and Compute Instance. See our Getting Started with Linode and Creating a Compute Instance guides.

2. Follow our Setting Up and Securing a Compute Instance guide to update your system. You may also wish to set the timezone, configure your hostname, create a limited user account, and harden SSH access.

What is sd?

sd is a find-and-replace tool that uses a common regular expression (regex) syntax. This makes sd adaptable to pretty much any text search need. sd’s common regex is popular and well-documented, so you also avoid the headaches of potentially quirky regex variants like the one used by sed.

For that reason, sd stands out as an alternative for the most common use of the sed command, finding and replacing text. And, by focusing exclusively on that function, sd additionally streamlines its command structure. sd commands are much more intuitive and readable than sed commands, letting you put more focus on constructing your search patterns.

sd was built using Rust, and, like many tools taking advantage of the Rust environment, it shows in sd’s remarkable performance. In the developer’s benchmarks, sd handily outperforms sed on complex substitution tasks.

How to Install sd

1. Install gcc.

   • On Debian and Ubuntu, you can do so with:

       sudo apt install build-essential
     

   • On AlmaLinux, CentOS (8 or later), and Fedora, use:

       sudo dnf install gcc
     

2. Install Rust, which includes the Cargo package manager used to install sd:

    curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
   

   When prompted, select 1 for the default installation path.

3. Either restart your shell session (exiting and logging back in) or run the following command:

    source $HOME/.cargo/env
   

4. Install sd via the Cargo package manager:

    cargo install sd
   

5. You can then verify your installation with:

    sd --version
   

   sd 0.7.6
       

How to Use sd

The sd command’s syntax is straightforward. The sections below discuss the basics of using sd, and how its commands compare to sed commands. You also learn how you can take advantage of regex syntax in sd for more advanced searches.

Basic Usage Compared to sed

Because it’s only focused on finding and replacing strings, the essential syntax for sd is considerably simpler than the syntax for sed. In sed, here’s what the skeleton of a substitution command looks like:

sed -e 's/{string to find}/{string to substitute}/g'

Whereas, in sd, the same function works as follows:

sd '{string to find}' '{string to substitute}'

The difference may not look too big, but sed only adds complexity as you start working with the actual strings. For instance, to substitute a literal URL with sed, you need the following commands:

echo 'Learn about a great find-and-replace tool here: https://www.gnu.org/software/sed/manual/sed.html' \
| sed -e 's/https\:\/\/www\.gnu\.org\/software\/sed\/manual\/sed\.html/https\:\/\/github\.com\/chmln\/sd/g'

Learn about a great find-and-replace tool here: https://github.com/chmln/sd

You can use sed’s option to change delimiters, using a , instead of a /, as in:

echo 'Learn about a great find-and-replace tool here: https://www.gnu.org/software/sed/manual/sed.html' \
| sed -e 's,https://www.gnu.org/software/sed/manual/sed.html,https://github.com/chmln,g'

But the long, unbroken string still comes across as difficult to parse.

Meanwhile, the same substitution in sd is much more concise:

echo 'Learn about a great find-and-replace tool here: https://www.gnu.org/software/sed/manual/sed.html' \
| sd -s 'https://www.gnu.org/software/sed/manual/sed.html' 'https://github.com/chmln/sd'

The -s option tells sd to read the input strings literally, special characters and all. It’s a great option for simple substitutions, when you don’t need the robust power of regex.

More Advanced Usage with Regex

Of course, use of a common regex syntax is one of the major advantages of sd. It allows for complicated and elegant search patterns with a widely-used and well-documented syntax, without particular quirks.

To give you a practical example, this guide uses a code file from the NeoVim project. You can use the following command to download the file and follow along:

curl -O https://raw.githubusercontent.com/neovim/neovim/master/src/nvim/main.c

You can now have sd find all functions/methods that return void and that have their initial curly braces on a new line. Then, have sd move those curly braces onto the same line as the method declaration:

cat nvim-main.c | sd '(void .*)\((.*)\).*\n\s*\{' '$1($2) {'

void event_init(void) {
// [...]
static void command_line_scan(mparm_T *parmpo) {
// [...]
static void check_swap_exists_action(void gogogo) {
// [...]

Notice that the regex pattern above has several additional parentheses. These allow sd to select certain parts of the pattern for reuse in the replacement text. You can see these numbered $1 and $2 based on their order of occurrence.

The above pipes input text to sd, and sd outputs its results to the command line. This approach is great for trying out search patterns and seeing what works before committing to it.

But, when you’re ready, you can easily have sd make its substitutions directly to the file, like this:

sd '(void .*)\((.*)\).*\n\s*\{' '$1($2) {' main.c

Again for comparison, the equivalent of the above in sed comes out to:

sed -i -e ':q;N;s/\(void .*\)(\(.*\)).*\n\s*{/\1(\2 gogogo) {/g' main.c

Which is not only significantly less readable, but also significantly different than standard regex patterns. Thus, more complicated search patterns in sed tend to take a lot more research and experimentation to get right. And the above sed command still fails to recognize many of the instances it was expected to.

Conclusion

At its core, sd is simple and consistent, and yet also powerful and capable of handling a variety of complex substitutions. Because it uses common regex, you have a wealth of comments and documentation around to help you work out whatever patterns you need.

To get started learning more about regex syntax, take a look at the regex cheat sheet provided by Mozilla.

More Information

You may wish to consult the following resources for additional information on this topic. While these are provided in the hope that they will be useful, please note that we cannot vouch for the accuracy or timeliness of externally hosted materials.

• GitHub: chmln/sd