Scanln

Scanln is a function in the Go programming language’s standard library, within the fmt package. It reads input from standard input and assigns the scanned values to the provided variables. The function signature is func Scanln(a ...*T) (n int, err error), where a is a list of pointers to the destinations for the scanned values. It treats whitespace as a separator and reads input up to and including a newline, stopping after the newline has been read. The number of successfully scanned items is returned as n, along with any error encountered as err.

In practice, Scanln is used to obtain simple, line-oriented input from the user. Values are scanned in the order of the supplied destinations and must be compatible with the respective types (for example, a string destination will store a word or token, an int destination will parse a number, etc.). The function waits for the user to press Enter to complete the line, making it straightforward for interactive prompts but less suited to complex input parsing.

If the input line contains tokens that do not match the expected types, an error is returned and scanning stops. If the input ends before a newline is read, an error such as io.EOF may be returned. Any input beyond what the destinations can hold may remain unread in the input buffer.

Scanln is one of several related functions in the fmt package for input: it shares behavior patterns with Scan and Scanf, and there are reader-based variants such as Fscan and Fscanln for scanning from an io.Reader instead of standard input.