I don't think so.
When I close the file and don't explicitly flush:
package main
import (
"bufio"
"fmt"
"io"
"os"
)
func main() {
sourceFilename := "MozillaFirefox-66.0.5-741.4.x86_64.rpm"
sourcef, err := os.Open(sourceFilename)
if err != nil {
fmt.Println("Error while opening source file:", err)
return
}
defer sourcef.Close()
destinationFilename := "CopiedMozillaFirefox-66.0.5-741.4.x86_64.rpm"
os.Create(destinationFilename)
destf, err := os.OpenFile(destinationFilename, os.O_APPEND|os.O_WRONLY,
os.ModeAppend)
if err != nil {
fmt.Println("Error while opening destination file:", err)
return
}
defer func() {
fmt.Println("Closing file.")
destf.Close()
}()
fReader := bufio.NewReader(sourcef)
fWriter := bufio.NewWriter(destf)
n, err := io.Copy(fWriter, fReader)
if err != nil {
fmt.Println("Error while copying:", err)
return
}
fmt.Println("Copied", n, "bytes.")
}
Output:
➜ throttle-and-resume-download go run copyTest.go
Copied 46061104 bytes.
Closing file.
➜ throttle-and-resume-download diff MozillaFirefox-66.0.5-741.4.x86_64.rpm
CopiedMozillaFirefox-66.0.5-741.4.x86_64.rpm
Binary files MozillaFirefox-66.0.5-741.4.x86_64.rpm and
CopiedMozillaFirefox-66.0.5-741.4.x86_64.rpm differ
➜ throttle-and-resume-download echo $?
1
When I explicitly flush:
package main
import (
"bufio"
"fmt"
"io"
"os"
)
func main() {
sourceFilename := "MozillaFirefox-66.0.5-741.4.x86_64.rpm"
sourcef, err := os.Open(sourceFilename)
if err != nil {
fmt.Println("Error while opening source file:", err)
return
}
defer sourcef.Close()
destinationFilename := "CopiedMozillaFirefox-66.0.5-741.4.x86_64.rpm"
os.Create(destinationFilename)
destf, err := os.OpenFile(destinationFilename, os.O_APPEND|os.O_WRONLY,
os.ModeAppend)
if err != nil {
fmt.Println("Error while opening destination file:", err)
return
}
defer func() {
fmt.Println("Closing file.")
destf.Close()
}()
fReader := bufio.NewReader(sourcef)
fWriter := bufio.NewWriter(destf)
n, err := io.Copy(fWriter, fReader)
if err != nil {
fmt.Println("Error while copying:", err)
return
}
// Flush writer to ensure all contents are written to file
err = fWriter.Flush()
if err != nil {
fmt.Println("Error while flushing writer:", err)
return
} else {
fmt.Println("Flushed writer.")
}
fmt.Println("Copied", n, "bytes.")
}
Output:
➜ throttle-and-resume-download go run copyTest.go
Flushed writer.
Copied 46061104 bytes.
Closing file.
➜ throttle-and-resume-download diff MozillaFirefox-66.0.5-741.4.x86_64.rpm
CopiedMozillaFirefox-66.0.5-741.4.x86_64.rpm
➜ throttle-and-resume-download echo $?
0
On Tuesday, May 21, 2019 at 6:39:08 PM UTC+5:30, Robert Engels wrote:
>
> You do not need to flush if you call close. Close will flush. There is
> some other bug in your code I believe.
>
> > On May 21, 2019, at 3:01 AM, Jan Mercl <0xj...@gmail.com <javascript:>>
> wrote:
> >
> >> On Tue, May 21, 2019 at 9:44 AM <pierr...@gmail.com <javascript:>>
> wrote:
> >>
> >> Usually though, you do not need to buffer the input or output at all.
> >
> > If I/O is performed in chunks comparable in size to what
> > bufio.{Reader,Writer} uses then ok. When I/O is done in small chunks,
> > then using bufio should improve performance.
> >
> > The question left is what the "usual" scenario is.
> >
> > --
> > You received this message because you are subscribed to the Google
> Groups "golang-nuts" group.
> > To unsubscribe from this group and stop receiving emails from it, send
> an email to golan...@googlegroups.com <javascript:>.
> > To view this discussion on the web visit
> https://groups.google.com/d/msgid/golang-nuts/CAA40n-WsWkLtnP19DUwHNSrjDNBncbVepqNxVj%3DUF6MFV8ARLA%40mail.gmail.com.
>
>
> > For more options, visit https://groups.google.com/d/optout.
>
>
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