FScan

Fscan is a function in the Go programming language, part of the fmt package, that reads formatted input from an io.Reader and stores the extracted values into the provided variables. It uses the same set of formatting verbs as other fmt scanning operations to determine how to parse the input. The function signature is Fscan(r io.Reader, a ...interface{}) (n int, err error). It returns the number of successfully assigned values and any error encountered during scanning.

Input for Fscan is read from the specified reader token by token, with whitespace serving as the default delimiter between tokens. Scanning continues as long as tokens can be parsed into the corresponding variables. If a token cannot be parsed into the supplied variable, the scan stops and an error is returned. If no tokens are scanned before the end of the input, Fscan returns 0 and an error, typically io.EOF or another scanner-related error.

Common usage involves passing a reader such as os.Stdin or a buffered reader created with bufio.NewReader. The arguments after the reader are pointers to variables where the scanned values will be stored, for example, integers, strings, booleans, or other types that implement the scanning interface.

Fscan is often used for reading structured input from files or standard input in Go programs. It is related to other fmt scanning functions such as Fscanln, which behaves similarly but stops scanning at a newline, and Fscanf, which uses a format string with verbs to control parsing more precisely.