Can You Escape the Go `bufio.Scanner` Input Loop Without a Conditional Check?

Escape the Input Loop without Conditional Check

In Go, the bufio.Scanner allows you to read input from the console line by line. However, the standard Scan function automatically advances to the next token, potentially resulting in an infinite loop if there's no explicit break condition.

The documentation states that Scan returns false when it reaches the end of the input. Does this mean you can skip the conditional check for breaking out of the loop?

Doc Misinterpretation

Unfortunately, you misinterpreted the documentation. The default split function used by the Scanner is ScanLines, which returns each line of text as a separate token.

Behavior of ScanLines

ScanLines has two key behaviors:

1. Empty Line Returns: It can return empty lines, even consecutive ones, without affecting the flow of the loop.
2. Non-Empty Line without Newline: The final non-empty line of the input will be returned even if it doesn't have a newline character.

Breaking the Loop

Therefore, an empty line alone does not signal the end of the input. The loop will only break when you reach an end-of-file (EOF) condition, typically triggered by actions like pressing Ctrl-D.

Solution

To escape the input loop without an if-clause, you must either:

• Manually handle the case of an empty line by checking input.Text() == ""
• Use a custom split function that returns false when it encounters an empty line

However, it's generally recommended to keep the conditional check for simplicity and to avoid potential edge cases.

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