This article will provide examples and explanations for different use cases of the ‘dlv’ command, which is a debugger for the Go programming language. The ‘dlv’ command is used for compiling and debugging Go programs, connecting to a headless debug server, attaching to a running process for debugging, and compiling and tracing a program.

Use case 1: Compile and begin debugging the main package in the current directory

Code:

dlv debug

Motivation: This use case is helpful when you want to compile and debug the main package in your current directory. It allows you to step through the code and inspect the variables to track down bugs or understand the program’s behavior.

Explanation: The command ‘dlv debug’ is used to compile and begin debugging the main package in the current directory. By default, it starts the debugger with no arguments.

Example Output:

Type 'help' for list of commands.
(dlv)

Use case 2: Compile and begin debugging a specific package

Code:

dlv debug package arguments

Motivation: Sometimes you may want to debug a specific package instead of the main package. This use case allows you to specify the package and any additional arguments required for compilation.

Explanation: In this use case, the ‘dlv debug’ command is used to compile and begin debugging a specific package. ‘package’ should be replaced with the name of the Go package you want to debug, and ‘arguments’ can be any additional arguments required for compilation.

Example Output:

Type 'help' for list of commands.
(dlv)

Use case 3: Compile a test binary and begin debugging the compiled program

Code:

dlv test

Motivation: When writing tests for Go programs, it can be helpful to debug the test binary itself. This use case allows you to compile the test binary and start debugging it.

Explanation: The ‘dlv test’ command is used to compile a test binary and begin debugging the compiled program. It is specifically designed for debugging test binaries and provides the ability to step through the test code and inspect variables.

Example Output:

Type 'help' for list of commands.
(dlv)

Use case 4: Connect to a headless debug server

Code:

dlv connect ip_address

Motivation: In some cases, you may have a headless debug server running on a remote machine or in a container. This use case allows you to connect to the headless debug server and perform debugging remotely.

Explanation: The ‘dlv connect’ command is used to connect to a headless debug server. ‘ip_address’ should be replaced with the IP address or hostname of the machine where the debug server is running.

Example Output:

Connected to <ip_address>:<port>
Type 'help' for list of commands.
(dlv)

Use case 5: Attach to a running process and begin debugging

Code:

dlv attach pid

Motivation: There may be cases where you want to attach a debugger to a running Go application and debug it live. This use case allows you to attach to a running process and start debugging it.

Explanation: The ‘dlv attach’ command is used to attach to a running process and begin debugging. ‘pid’ should be replaced with the process ID of the running Go application.

Example Output:

Type 'help' for list of commands.
(dlv)

Use case 6: Compile and begin tracing a program

Code:

dlv trace package --regexp 'regular_expression'

Motivation: Tracing a program can be useful for understanding its execution flow and identifying performance bottlenecks. This use case allows you to compile and begin tracing a specific Go package using regular expressions to filter the traced functions.

Explanation: In this use case, the ‘dlv trace’ command is used to compile and begin tracing a program. ‘package’ should be replaced with the name of the Go package you want to trace, and ‘–regexp’ is used to specify a regular expression to filter the traced functions.

Example Output:

Tracing <package>
Type 'exit' to stop tracing.
(dlv)

Conclusion:

The ‘dlv’ command is a powerful debugger for the Go programming language. It provides various use cases for debugging, connecting to a debug server, attaching to running processes, and tracing programs. By following the examples and explanations in this article, you can effectively use the ‘dlv’ command to debug and trace your Go applications.