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Question

I am writing a simple script to get download unzip the tar.gz file and then remove it. Whenever I try to remove it I get an error: The process cannot access the file because it is being used by another process.

I assume the error is in how I pass the file to the extractTarGz function, but I am not sure.

Here is the code:

package main

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

func main() {
    f, err := os.Open("file.tar.gz")
    if err != nil {
        panic(err)
    }
    defer f.Close()
    extractTarGz(f)

    err = os.Remove("file.tar.gz")
}

func extractTarGz(gzipStream io.Reader) {
    uncompressedStream, err := gzip.NewReader(gzipStream)
    if err != nil {
        log.Fatal("ExtractTarGz: NewReader failed")
    }

    tarReader := tar.NewReader(uncompressedStream)

    for true {
        header, err := tarReader.Next()

        if err == io.EOF {
            break
        }

        if err != nil {
            log.Fatalf("ExtractTarGz: Next() failed: %s", err.Error())
        }

        switch header.Typeflag {
        case tar.TypeDir:
            if err := os.Mkdir(header.Name, 0755); err != nil {
                log.Fatalf("ExtractTarGz: Mkdir() failed: %s", err.Error())
            }
        case tar.TypeReg:
            outFile, err := os.Create(header.Name)
            if err != nil {
                log.Fatalf("ExtractTarGz: Create() failed: %s", err.Error())
            }
            defer outFile.Close()
            if _, err := io.Copy(outFile, tarReader); err != nil {
                log.Fatalf("ExtractTarGz: Copy() failed: %s", err.Error())
            }
        default:
            log.Fatalf(
                "ExtractTarGz: uknown type: %s in %s",
                header.Typeflag,
                header.Name)
        }
    }
}

Answer 1

You should first close the file, and then attempt to remove it. Since you close it using defer, that will / would be called after the os.Remove() call.

Try it like this:

name := "file.tar.gz"
defer func() {
    if err = os.Remove(name); err != nil {
        log.Printf("Failed to remove %s: %v", name, err)
    }
}()

f, err := os.Open(name)
if err != nil {
    panic(err)
}
defer f.Close()

extractTarGz(f)

Deferred functions are executed in LIFO (last-in-first-out) order, so first f.Close() will be called, and then the other which tries to remove the file. Quoting from Spec: Deferred statements:

...deferred functions are invoked immediately before the surrounding function returns, in the reverse order they were deferred.