On Thu, Nov 2, 2017 at 10:37 AM, Jon Forrest <nob...@gmail.com> wrote:
>
> I'm learning Go. Whenever I learn a new programming language I like to try
> to recreate the Unix 'ls' command
> in that language. I've found that such an exercise is often a good way to
> get familiar with what a language offers.
>
> Here's my environment:
>
> $ go version
> go version go1.9.2 linux/amd64
> $ cat /etc/redhat-release
> CentOS Linux release 7.4.1708 (Core)
>
> Consider the following trivial program which I've saved as "ls.go":
>
> package main
>
> import (
> "fmt"
> "os"
> )
>
> func main() {
> for _, arg := range os.Args[1:] {
> fi, err := os.Stat(arg)
> if err != nil {
> fmt.Println(err)
> return
> }
> switch mode := fi.Mode(); {
> case mode.IsRegular():
> fmt.Println("regular file")
> case mode.IsDir():
> fmt.Println("directory")
> }
> }
> }
>
>
> When I run 'go build ls.go' and then './ls ls.go' I see the output I expect,
> which is
> 'regular file'.
>
> However, when I run 'go run ls.go ls.go' I get the bizarre message
>
> can't load package: package main: case-insensitive file name collision:
> "ls.go" and "ls.go"
>
> This is on an xfs filesystem.
>
> I don't understand why this error message appeared, nor what it's trying to
> tell me.
> Plus, I don't understand why running the result of 'go build' works, but
> building
> and running the program using 'go run' fails.
`go run` takes multiple files as arguments. When you type `go run
ls.go ls.go` you are asking the go tool to build a Go program that
consists of the contents of ls.go repeated twice. Before it even gets
to that point, it says "wait, you've told me the same file name twice,
that can't be right" and then it starts talking about a
case-insensitive file name which is certainly confusing. This is kind
of hard to avoid using `go run`, as it takes any argument that ends
with ".go" as meaning a Go file to compile.
Ian
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