How to Use the `perldoc` Command (with Examples)

perldoc is a command-line tool that provides access to Perl documentation, allowing users to read about Perl’s functions, variables, modules, and other components directly from the terminal. By fetching data from Perl’s POD (Plain Old Documentation) files, perldoc makes it easy for developers to quickly find the information they need without leaving their coding environment. Whether you’re learning a new function or trying to understand a configuration file, perldoc offers a quick and efficient way to retrieve comprehensive documentation.

Use case 1: View documentation for a builtin function, a variable, or an API

Code:

perldoc -f|v|a name

Motivation:

As a Perl developer, you often need immediate access to detailed information about functions, variables, or APIs while writing or debugging code. Instead of combing through extensive online resources or flipping through books, using perldoc with the -f, -v, or -a options allows you to directly access specific documentation from the command line. This can significantly speed up your workflow and provide accurate, reliable information.

Explanation:

• -f: This flag is used to specify that you are looking for documentation on a builtin function.
• -v: This flag is used to search for documentation on a Perl variable.
• -a: This is used when you need the documentation for a specific API.
• name: Here, you replace ’name’ with the actual name of the function, variable, or API you wish to learn more about.

Example Output:

If you run perldoc -f print, you might receive:

print FILEHANDLE LIST
print LIST
print    Prints a string or a list of strings. By default, the function begins
         printing at the current cursor position.
...

Use case 2: Search in the question headings of Perl FAQ

Code:

perldoc -q regex

Motivation:

When dealing with ongoing challenges or common issues in Perl, accessing frequently asked questions (FAQs) saves time and provides insights from experienced developers. Instead of searching online forums, perldoc -q allows you to search directly within the well-curated Perl FAQs for specific topics or keywords like ‘regex’. This makes it easier to find solutions to recurring problems or learning points.

Explanation:

• -q: This flag specifies that you want to search through Perl’s FAQ question headings.
• regex: This is the search term used within the FAQ. In this instance, ‘regex’ is the term being searched for.

Example Output:

Running perldoc -q regex might yield:

Found in /.../perlfaq6.pod
  How do I use a regular expression to strip C-style comments from a file?
  How do I use a regular expression to detect a balanced set of parentheses?
  ...

Use case 3: Send output directly to stdout

Code:

perldoc -T page|module|program|URL

Motivation:

By default, perldoc sends its output to a pager, which allows for easy navigation through lengthy documentation pages. However, in situations where you need to process the output with other command-line tools or redirect it to a file, having the output sent directly to stdout from the start can be immensely useful. Using the -T option makes this possible without the need to involve a pager.

Explanation:

• -T: This flag directs perldoc to send the output directly to stdout instead of the default pager.
• page|module|program|URL: Specifies the page, module, program, or URL whose documentation should be accessed.

Example Output:

Executing perldoc -T perlintro could reveal text output directly into the terminal like:

NAME
    perlintro - a brief introduction and overview of Perl

DESCRIPTION
    This document is intended to give you a quick overview of the Perl
    programming language, along with pointers to further sources of
    information.
...

Use case 4: Specify the language code of the desired translation

Code:

perldoc -L language_code page|module|program|URL

Motivation:

Multilingual developers or those working in non-English environments often need documentation in their native language to better comprehend the technical details. The -L option in perldoc enables users to specify their preferred language, which facilitates better understanding and aids developers who might be more comfortable in a language other than English. This can also be beneficial in multilingual teams where documentation consistency across languages may be vital.

Explanation:

• -L: This flag sets the language code for the documentation’s translation, enabling viewing of the documentation in the specified language.
• language_code: This is the ISO language code representing the desired language for translation.
• page|module|program|URL: Indicates the specific documentation you want to retrieve.

Example Output:

If you executed perldoc -L fr perlsyn, the output would start with:

NOM
    perlsyn - Structures de contrôle de Perl

DESCRIPTION
    Ce document couvre les structures de contrôle de base de Perl.
...

Conclusion

The perldoc command is a versatile tool for Perl programmers, providing a convenient way to access comprehensive language documentation directly from the terminal. Whether you’re seeking information about specific functions, troubleshooting with FAQs, or needing documentation in another language, perldoc accommodates these needs efficiently. By mastering these diverse use cases and understanding their motivations, you can streamline your coding workflow and deepen your understanding of Perl.