The fmt.Fscanf
function in Golang is part of the fmt
package and is used to scan and read formatted input from an io.Reader
, such as a file or a buffer, based on a specified format string. This function allows you to parse input data according to format specifiers and store the parsed values in provided variables.
Table of Contents
- Introduction
Fscanf
Function Syntax- Examples
- Basic Usage
- Reading from a File
- Real-World Use Case
- Conclusion
Introduction
The fmt.Fscanf
function reads formatted input from an io.Reader
using a format string, which makes it more flexible and precise than fmt.Fscan
. It is particularly useful for parsing structured data from files, network connections, or other sources that implement the io.Reader
interface.
Fscanf Function Syntax
The syntax for the fmt.Fscanf
function is as follows:
func Fscanf(r io.Reader, format string, a ...interface{}) (n int, err error)
Parameters:
r
: Anio.Reader
from which the input is read.format
: A format string containing format specifiers that determine how to parse the input.a
: Pointers to variables where the scanned data will be stored.
Returns:
n
: The number of items successfully scanned and assigned.err
: An error if one occurred during scanning.
Examples
Basic Usage
This example demonstrates how to use the fmt.Fscanf
function to read formatted data from a string buffer.
Example
package main
import (
"bytes"
"fmt"
)
func main() {
// Create a buffer with some formatted data
data := "Name: John Age: 25"
buffer := bytes.NewBufferString(data)
var name string
var age int
// Use fmt.Fscanf to read data from the buffer
fmt.Fscanf(buffer, "Name: %s Age: %d", &name, &age)
// Print the scanned values
fmt.Printf("Name: %s, Age: %d\n", name, age)
}
Output:
Name: John, Age: 25
Reading from a File
You can use fmt.Fscanf
to read formatted data from a file.
Example
package main
import (
"fmt"
"os"
)
func main() {
// Open a file for reading
file, err := os.Open("product.txt")
if err != nil {
fmt.Println("Error opening file:", err)
return
}
defer file.Close()
var item string
var price float64
// Use fmt.Fscanf to read data from the file
_, err = fmt.Fscanf(file, "Item: %s Price: %f", &item, &price)
if err != nil {
fmt.Println("Error reading from file:", err)
return
}
// Print the scanned values
fmt.Printf("Item: %s, Price: %.2f\n", item, price)
}
Contents of product.txt
:
Item: Laptop Price: 1299.99
Output:
Item: Laptop, Price: 1299.99
Real-World Use Case
Parsing Configuration Files
In real-world applications, fmt.Fscanf
can be used to parse configuration files with a specific format.
Example
package main
import (
"bytes"
"fmt"
)
func main() {
// Simulate a configuration file with key-value pairs
configData := "host=localhost\nport=8080"
configFile := bytes.NewBufferString(configData)
var host string
var port int
// Use fmt.Fscanf to read configuration settings
fmt.Fscanf(configFile, "host=%s\nport=%d", &host, &port)
// Print the configuration settings
fmt.Printf("Host: %s\nPort: %d\n", host, port)
}
Output:
Host: localhost
Port: 8080
Conclusion
The fmt.Fscanf
function is a powerful way to read and parse formatted input from any io.Reader
using a format string. It is ideal for applications that need to process structured data from files, buffers, or network connections. By using fmt.Fscanf
, you can efficiently extract and parse data from various sources in your Go programs.
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