1.1 hello, world
helloworld.go
package main
import "fmt"
func main() {
fmt.Println("Hello, World")
}
Execute go run helloworld.goRun the program.
Build and execute.
go build helloworld.go
./helloworld
1.2 Command line parameters
The variable os.Args is a string slice.
echo1.go
package main
import (
"fmt"
"os"
)
func main() {
var s, sep string
for i := 1; i < len(os.Args); i++ {
s += sep + os.Args[i]
sep = " "
}
fmt.Println(s)
}
If a variable is not initialized when declared, it will be implicitly initialized to a null value of this type. For example, the initialization result is 0 for numbers and the empty string "" for strings.
for is the only loop statement in Go. There are several forms.
for initialization; condition; post { // zero or more statements }
// Traditional "while" loop
for condition { // }
// Traditional infinite loop
for { // … }
Another form of for loop iterates over string or slice data.
echo2.go
package main
import (
"fmt"
"os"
)
func main() {
s, sep := "", ""
for _, arg := range os.Args[1:] {
s += sep + arg
sep = " "
}
fmt.Println(s)
}
The following ways of declaring string variables are equivalent:
s := ""
var s string
var s = ""
var s string = ""
echo3.go
package main
import (
"fmt"
"os"
)
func main() {
fmt.Println(strings.Join(os.Args[1:], " "))
}