How to use the command 'errno' (with examples)

The errno command is used to look up errno names and descriptions. It provides information about error codes and their corresponding descriptions. This can be useful when troubleshooting and debugging programs, as it helps to understand the meaning of error codes.

Use case 1: Lookup errno description by name or code

Code:

errno name|code

Motivation: The motivation for using this example is to quickly find the description of a specific errno name or code. This can be helpful when encountering an error in a program and needing to understand what the error code means.

Explanation: The name|code argument can be either an errno name or an errno code. It is used to specify the specific errno for which you want to retrieve the description.

Example output:

$ errno EACCES
EACCES      13      Permission denied

In this example, the errno command is used to look up the description for the errno code EACCES. The output displays the name, code, and description of the errno.

Use case 2: List all errno names, codes, and descriptions

Code:

errno --list

Motivation: The motivation for using this example is to obtain a comprehensive list of all errno names, codes, and descriptions. This can be useful for reference or when dealing with error handling in programs.

Explanation: The --list argument is used to instruct the errno command to display a list of all errno names, codes, and descriptions.

Example output:

$ errno --list
EPERM       1       Operation not permitted
ENOENT      2       No such file or directory
...

In this example, the errno command with the --list argument is used to retrieve a list of all errno names, codes, and descriptions. The output displays each errno entry with its corresponding name, code, and description.

Use case 3: Search for code whose description contains all of the given text

Code:

errno --search text

Motivation: This example is useful when you want to search for specific error codes based on a particular description. It helps to quickly locate relevant error codes that match the given text.

Explanation: The --search argument is used with the errno command to perform a search for error codes whose description contains all of the given text.

Example output:

$ errno --search "permission denied"
EACCES      13      Permission denied
EPERM       1       Operation not permitted

In this example, the errno command is used with the --search argument to search for error codes with descriptions that contain the text “permission denied”. The output displays the matching error codes along with their names, codes, and descriptions.

Use case 4: Search for code whose description contains all of the given text (all locales)

Code:

errno --search-all-locales text

Motivation: This example is similar to the previous use case, but it searches for error codes based on the description text in all locales. This can be useful when dealing with programs or systems that use different locales.

Explanation: The --search-all-locales argument is used to perform a search for error codes whose description contains all of the given text, considering all available locales.

Example output:

$ errno --search-all-locales "permission denied"
EACCES      13      Permission denied
EPERM       1       Operation not permitted

In this example, the errno command with the --search-all-locales argument is used to search for error codes with descriptions that contain the text “permission denied” in all locales. The output displays the matching error codes along with their names, codes, and descriptions.

Conclusion:

The errno command is a helpful tool for looking up errno names and descriptions. It provides an easy way to retrieve information about error codes, which can aid in troubleshooting and understanding program errors. Whether you need to look up a specific errno or obtain a comprehensive list, the errno command has you covered.