io.NewSectionReader() Function in Golang with Examples
Last Updated :
05 May, 2020
In Go language, io packages supplies fundamental interfaces to the I/O primitives. And its principle job is to enclose the ongoing implementations of such king of primitives. The NewSectionReader() function in Go language is used to return a SectionReader that reads from the stated reader “r” which starts at the stated offset “off” and terminates with the EOF i.e, end of file after the given “n” number of bytes. Moreover, this function is defined under the io package. Here, you need to import the “io” package in order to use these functions.
Syntax:
func NewSectionReader(r ReaderAt, off int64, n int64) *SectionReader
Here, “r” is the reader from where the content is read, “off” is the stated offset from where the content reading starts, and “n” is the number of bytes till which the content is read.
Return value: It returns a “SectionReader” that reads from the stated reader “r” which starts at the stated offset “off” and terminates with the EOF i.e, end of file after the given “n” number of bytes.
Below examples illustrates the use of above method:
Example 1:
package main
import (
"fmt"
"io"
"os"
"strings"
)
func main() {
reader := strings.NewReader( "Geeks\n" )
r := io.NewSectionReader(reader, 3, 5)
Reader, err := io.Copy(os.Stdout, r)
if err != nil {
panic(err)
}
fmt.Printf( "n: %v\n" , Reader)
}
|
Output:
ks
n: 3
In the above example, Copy() method is used in order to return the output, and NewReader() method of strings is used from where the content to be read is written.
Example 2:
package main
import (
"fmt"
"io"
"os"
"strings"
)
func main() {
reader := strings.NewReader( "GeeksforGeeks\nis\na\nCS-Portal.\n" )
r := io.NewSectionReader(reader, 7, 40)
Reader, err := io.Copy(os.Stdout, r)
if err != nil {
panic(err)
}
fmt.Printf( "n: %v\n" , Reader)
}
|
Output:
rGeeks
is
a
CS-Portal.
n: 23
Here, the content starts from the offset “7” and terminates after the number of bytes reaches “40”. But in the output returned here the content copied is of “23” bytes so “n” is 23.
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