Read contents of tar file without unzipping to disk

Question

I have been able to loop through the files in a tar file, but I am stuck on how to read the contents of those files as string. I would like to know how to print the contents of the files as a string?

This is my code below

package main

import (
    "archive/tar"
    "fmt"
    "io"
    "log"
    "os"
    "bytes"
    "compress/gzip"
)

func main() {
    file, err := os.Open("testtar.tar.gz")

    archive, err := gzip.NewReader(file)

    if err != nil {
        fmt.Println("There is a problem with os.Open")
    }
    tr := tar.NewReader(archive)

    for {
        hdr, err := tr.Next()
        if err == io.EOF {
            break
        }
        if err != nil {
            log.Fatal(err)
        }

        fmt.Printf("Contents of %s:\n", hdr.Name)
    }
}

Answer 1

Just use the tar.Reader as an io.Reader for each file you want to read.

tr := tar.NewReader(r)

// get the next file entry 
h, _ := tr.Next() 

If you need the whole file as a string:

// read the complete content of the file h.Name into the bs []byte
bs, _ := ioutil.ReadAll(tr)

// convert the []byte to a string
s := string(bs)

If you need to read line by line, then this would be better:

// create a Scanner for reading line by line
s := bufio.NewScanner(tr)

// line reading loop
for s.Scan() {

  // read the current last read line of text
  l := s.Text()

  // ...and do something with l

}

// you should check for error at this point
if s.Err() != nil {
  // handle it
}

Answer 2

With some help from the official site this is what I had intended previously. Special focus should be turned to the bottom where the conversion from bytes to string is made.

package main

import (
    "archive/tar"
    "fmt"
    "io"
    "log"
    "os"
    "bytes"
    "compress/gzip"
)

func main() {

    file, err := os.Open("testtar.tar.gz")

    archive, err := gzip.NewReader(file)

    if err != nil {
        fmt.Println("There is a problem with os.Open")
    }
    tr := tar.NewReader(archive)

    for {
        hdr, err := tr.Next()
        if err == io.EOF {
            break
        }
        if err != nil {
            log.Fatal(err)
        }

        fmt.Printf("Contents of %s:\n", hdr.Name)

        //Using a bytes buffer is an important part to print the values as a string

        bud := new(bytes.Buffer)
        bud.ReadFrom(tr)
        s := bud.String()
        fmt.Println(s)
        fmt.Println()
    }

}