I have a command line programme that can output to either stdout or a named
file. Output to stdout, as commented out in the small example below, works
fine, but not to a named file.
Attempting to write to a named file panics on go 1.17 on Linux with:
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0x46123d]
I'm confused since both os.Stdout and os.Create are *os.File types, which
implement the Write(b []byte) (n int, err error) method which fulfils the
io.Writer interface. I pass around io.Writer types in my programme to
facilitate testing.
I've chosen io.WriteString because it will use StringWriter on the writer if
the writer supports this method, which may perform better than a simple Write.
Clearly I am missing something fundamental, or I have a stupid error in my
programme. Help very much appreciated.
Thanks
Rory
package main
import (
"io"
"log"
"os"
)
func main() {
// o := "-" // use stdin
o := "/tmp/output.txt" // or a file
var output io.Writer
if o == "-" {
output = os.Stdout
} else {
output, err := os.Create(o)
if err != nil {
log.Fatalf("Could not create file %s, %s", output, err)
}
defer output.Close()
}
_, err := io.WriteString(output, "hello")
if err != nil {
log.Fatal(err)
}
}
--
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 golang-nuts+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/golang-nuts/YlUv/%2BH%2BHYguq4Nn%40campbell-lange.net.
