A ‘for loop’ is a golang statement which allows code to be repeatedly executed. A for loop is classified as an iteration statement i.e. it is the repetition of a process within a go program. For example, you can run certain task or print message five times or read & process list of files using a for loop. Golang for loop is similar to but not the same as—C’s for loop syntax.
go lang for loop syntax
The basic syntax is:
for init; condition; post {
// run commands till condition is true
}
Infinite for loop syntax:
for {
// I will run forever
}
go lang for loop examples
The following golang program print welcome message five times using a for loop. Create a file called for.go:
// for.go : A simple for loop program written in golang
package main
// get fmt package for Printf()
import "fmt"
// Our main()
func main() {
// set a for loop
for i := 1; i
Save and close the file. Run it as follows:
$ go run for.go
Sample outputs:
Welcome 1 times
Welcome 2 times
Welcome 3 times
Welcome 4 times
Welcome 5 times
Here is another example to print sum of all digits using a for loop:
// sum.go : golang for loop demo code
package main
import "fmt"
func main() {
sum := 0
for i := 1; i
Save and close the file. Run it as follows:
$ go run sum.go
Sample outputs:
Sum = 210
How do I use golang for as infinite loops?
Infinite for loop can be created with empty expressions, such as:
// forver-in-love.go : an infinite loop example
package main
import "fmt"
func main() {
for {
fmt.Println("I am in love with the Terminal (hit Ctrl+C to stop)")
}
}
In this example, read an integer (number) from keyboard and display message on screen:
// for2.go : A modified version of for.go. This program use Scan() to read input from user
package main
import "fmt"
func main() {
y := 0
// Get number from user
fmt.Printf("Enter a number : ")
fmt.Scan(&y)
for i := 1; i
Sample outputs:
$ go run for2.go
Enter a number : 3
Welcome 1 times.
Welcome 2 times.
Welcome 3 times.
How do I terminate a for loop using break keyword?
You need to use the break keyword and the syntax is as follows:
for .... {
if condition { break }
}
In this example, break out of for loop when i is 5:
//
// forbreakdemo.go : Terminate a loop using break keyword
//
package main
// get fmt package for Printf()
import "fmt"
// Our main()
func main() {
// set a for loop
for i := 1; i<=10; i++ {
//break out of for loop when i greater than 5
if i > 5 { break }
fmt.Printf("Welcome %d times\n",i)
}
fmt.Printf("Out of for loop...\n")
}
How do I go to the beginning of the for loop?
You need to use the continue keyword and the syntax is as follows:
for ... {
statement_1
if condition { continue }
statement_2
}
In this example, print message only if i is not 5:
// forcontinuedemo.go : The continue keyword demo
package main
// get fmt package for Printf()
import "fmt"
// Our main()
func main() {
// set a for loop
for i := 1; i<=10; i++ {
// only print welcome message if i is not 5
if i != 5 { continue }
fmt.Printf("Welcome %d times\n",i)
}
fmt.Printf("Outof for loop...\n")
}
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Very helpful examples… I was wondering if it is also possible to have 2 variables in a for loop in go.
Something like for i,j := 0,0 ; i < len(a) ; i++, j– ??
you can use one variable for the loop, then use the change in your looping variable to calculate two new variables i*A and i(-1)*B