Get current file name after creating executable - go

I can get the current directory and the name of the current .go file but if i build a .exe from the file with go build then i still get the .go name.
.../Project/Test/testfile.go
After building testfile.go with go build i have these:
1) .../Project/Test/testfile.go
2) .../Project/Test/main.exe
When i execute main.exe i get testfile But i want to get the main name after executing main.exe
package main
import (
"errors"
"fmt"
"path/filepath"
"runtime"
"strings"
)
func GetFileName() string {
_, fpath, _, ok := runtime.Caller(0)
if !ok {
err := errors.New("failed to get filename")
panic(err)
}
filename := filepath.Base(fpath)
filename = strings.Replace(filename, ".go", "", 1)
return filename
}
func main() {
fmt.Print(GetFileName())
}

The os package provides os.Args[0] to obtain the executable name, or if you want the whole path you could use os.Executable, as #Peter has suggested

Related

exec : hangman.go Executable file not found in $PATH

i have problem trying to run my hangman game (hangman.go) into an other program (server.go)
package main
import (
"log"
"os/exec"
)
func main() {
cmd := exec.Command("hangman.go")
err := cmd.Run()
if err != nil {
log.Fatal(err)
}
}
Ive tried to build a hangman.exe too but i still have the same error when i run server.go
2021/12/03 10:42:19 exec: "hangman.go": executable file not found in $PATH
exit status 1
You have two problems:
You cannot execute a *.go source file, you must use your compiled hangman.exe.
If your command "contains no path separators" then exec.Command() looks for the command in your PATH environment variable, it is not in any of those directories so it is not run. You need to specify a relative or fully qualified path to the file, if it is in the current working directory this can just be .\hangman.exe (or ./hangman on unix like systems):
package main
import (
"log"
"os/exec"
)
func main() {
cmd := exec.Command(".\hangman.exe")
err := cmd.Run()
if err != nil {
log.Fatal(err)
}
}

go run command doesn't pick up non-go files in the same path

Folder structure:
- dev.env
- go.mod
- main.go
dev.env:
ENV="DEV"
PASSWORD="DEV!##$%"
main.go:
package main
import (
"fmt"
"log"
"os"
"path/filepath"
"github.com/joho/godotenv"
)
var environment string
func init() {
fmt.Println("ENV: ", environment)
dir, err := filepath.Abs(filepath.Dir(os.Args[0]))
if err != nil {
log.Fatal(err)
}
devEnvPath := filepath.Join(dir, "dev.env")
_ = godotenv.Load(devEnvPath)
}
func main() {
fmt.Println("PASSWORD", os.Getenv("PASSWORD"))
}
Command:
go run -ldflags="-X 'main.environment=DEV'" .
Output:
ENV: DEV
PASSWORD
It works with go build but curious why it doesn't work with go run
As a general rule, don't use go run unless in the most trivial of use cases - it is the most common footgun in the Go community.
As #Marc pointed out the error stems from the go run binary is built in a temporary directory. To keep things simple, just use a relative path in your directory. This will work for both go build & go run:
dir := "."
devEnvPath := filepath.Join(dir, "dev.env")
err := godotenv.Load(devEnvPath)
if err != nil {
log.Fatal(err)
}
As of Go 1.16, the simplest way to access files from the directory containing a package's source code is to use //go:embed and the embed package to embed those files into the compiled binary:
//go:embed dev.env
var devEnv string
func init() {
m, err := godotenv.Unmarshal(devEnv)
…
}

How do you get full paths of all files in a directory in Go?

I am using Go to iterate over all the files in a directory. This is how I am doing it:
package main
import (
"fmt"
"io/ioutil"
)
func main() {
printFiles(".")
}
func printFiles(dir string) {
fileInfos, err := ioutil.ReadDir(dir)
if err != nil {
fmt.Println("Error in accessing directory:", err)
}
for _, file := range fileInfos {
fmt.Printf("%T: %+v\n", file, file)
}
}
When I run this code, this is the output I get:
*os.fileStat: &{name:main.go sys:{FileAttributes:32 CreationTime:{LowDateTime:2993982878 HighDateTime:30613689} LastAccessTime:{LowDateTime:2993982878 HighDateTime:30613689} LastWriteTime:{LowDateTime:4004986069 HighDateTime:30613714} FileSizeHigh:0 FileSizeLow:320} pipe:false Mutex:{state:0 sema:0} path:C:\Users\Prakhar.Mishra\go\src\mistdatafilter\main.go vol:0 idxhi:0 idxlo:0}
I can see a property named path, but I can't access it (due to small case initial, I suppose?). Can anyone please tell me how to get full file path of all the files in a given folder?
If you want to see a full path, you should start with a full path. . is a relative path.
You can get the working path with os.Getwd
path, err := os.Getwd()
// handle err
printFiles(path)
The rest is simply appending the file name to the directory path. You should use the path/filepath package for that:
for _, file := range fileInfos {
fmt.Println(filepath.Join(path, file.Name())
}
You can also use the filepath.Abs method from the standard library
import (
"fmt"
"os"
"path/filepath"
)
files, _ = os.ReadDir(dir)
path, _ := filepath.Abs(dir)
for _, file := range files {
fmt.Println(filepath.Join(path, file.Name())
}
You already have the directory path simply append them to the file name something like:
files, err := ioutil.ReadDir(dirPath)
check(err)
for _, file := range files {
fmt.Println(dirPath + file.Name())
}

FilePaths in Go

So this is the example from Programming in Go by Mark Summerfield.
package main
import (
"fmt"
"io/ioutil"
"os"
"path/filepath"
"strings"
)
var britishAmerican = "british-american.txt"
func init() {
dir, _ := filepath.Split(os.Args[0])
britishAmerican = filepath.Join(dir, britishAmerican)
}
func main() {
rawBytes, err := ioutil.ReadFile(britishAmerican)
if err != nil {
fmt.Println(err)
}
text := string(rawBytes)
usForBritish := make(map[string]string)
lines := strings.Split(text, "\n")
fmt.Println(lines)
for _, line := range lines {
fields := strings.Fields(line)
if len(fields) == 2 {
usForBritish[fields[0]] = fields[1]
}
}
fmt.Println(usForBritish)
}
When I run this code with the init() func commented out, it works perfectly fine. If I leave it in I get this error:
open /var/folders/l6/rdqtyrfd303dw1cz8qvlfcvc0000gn/T/go- build652175567/command-line-arguments/_obj/exe/british-american.txt: no such file or directory exit status 1
My question is, why does the init() func not grab the file from the appropriate directory?
You change the variable britishAmerican in the init function. Without init(), the program looks in the current directory (no path given, only the file name). With init(), it looks in the path where the executable is (os.Args[0]). And with go run main.go, the directory with the executable is not the current working directory.
You should use go build to build the binary and then run it, or you should tell us what you want to achieve (as written by #RoninDev).
The MCVE I've mentioned could look like this:
package main
import (
"io/ioutil"
"log"
"os"
"path/filepath"
)
var filename = "foo.txt"
func init() {
// change to true and things break
if false {
dir, _ := filepath.Split(os.Args[0])
filename = filepath.Join(dir, filename)
}
}
func main() {
// requires a file 'foo.txt' in the current directory
_, err := ioutil.ReadFile(filename)
if err != nil {
log.Fatal(err)
}
}
It can (of course) be even shorter, but this should be enough for the others in the community to see what is going on.
It looks to me like the program is expecting a file called british-american.txt in the directory that the executable is in.
That is what the code in init() does - it finds the path the the executable and constructs a path to the dictionary relative to that.
I can see from your error message that you are using go run to run the code. This makes a temporary executable in /tmp and runs that. If you leave the init() code in then it will look for the dictionary in the /tmp directory and it won't find it. If you take the init() code out it will look for the dictionary in the current directory and it will succeed.
If you want to use it as the author intended then use go build to build a binary and then run it - that will work.

How to get the directory of the currently running file?

In nodejs I use __dirname . What is the equivalent of this in Golang?
I have googled and found out this article http://andrewbrookins.com/tech/golang-get-directory-of-the-current-file/ . Where he uses below code
_, filename, _, _ := runtime.Caller(1)
f, err := os.Open(path.Join(path.Dir(filename), "data.csv"))
But is it the right way or idiomatic way to do in Golang?
EDIT: As of Go 1.8 (Released February 2017) the recommended way of doing this is with os.Executable:
func Executable() (string, error)
Executable returns the path name for the executable that started the current process. There is no guarantee that the path is still pointing to the correct executable. If a symlink was used to start the process, depending on the operating system, the result might be the symlink or the path it pointed to. If a stable result is needed, path/filepath.EvalSymlinks might help.
To get just the directory of the executable you can use path/filepath.Dir.
Example:
package main
import (
"fmt"
"os"
"path/filepath"
)
func main() {
ex, err := os.Executable()
if err != nil {
panic(err)
}
exPath := filepath.Dir(ex)
fmt.Println(exPath)
}
OLD ANSWER:
You should be able to use os.Getwd
func Getwd() (pwd string, err error)
Getwd returns a rooted path name corresponding to the current directory. If the current directory can be reached via multiple paths (due to symbolic links), Getwd may return any one of them.
For example:
package main
import (
"fmt"
"os"
)
func main() {
pwd, err := os.Getwd()
if err != nil {
fmt.Println(err)
os.Exit(1)
}
fmt.Println(pwd)
}
This should do it:
import (
"fmt"
"log"
"os"
"path/filepath"
)
func main() {
dir, err := filepath.Abs(filepath.Dir(os.Args[0]))
if err != nil {
log.Fatal(err)
}
fmt.Println(dir)
}
Use package osext
It's providing function ExecutableFolder() that returns an absolute path to folder where the currently running program executable reside (useful for cron jobs). It's cross platform.
Online documentation
package main
import (
"github.com/kardianos/osext"
"fmt"
"log"
)
func main() {
folderPath, err := osext.ExecutableFolder()
if err != nil {
log.Fatal(err)
}
fmt.Println(folderPath)
}
I came from Node.js to Go. The Node.js equivalent to __dirname in Go is:
_, filename, _, ok := runtime.Caller(0)
if !ok {
return errors.New("unable to get the current filename")
}
dirname := filepath.Dir(filename)
Some other mentions in this thread and why they're wrong:
os.Executable() will give you the filepath of the currently running executable. This is equivalent to process.argv[0] in Node. This is not true if you want to take the __dirname of a sub-package.
os.Getwd() will give you the current working directory. This is the equivalent to process.cwd() in Node. This will be wrong when you run your program from another directory.
Lastly, I'd recommend against pulling in a third-party package for this use case. Here's a package you can use:
package current
// Filename is the __filename equivalent
func Filename() (string, error) {
_, filename, _, ok := runtime.Caller(1)
if !ok {
return "", errors.New("unable to get the current filename")
}
return filename, nil
}
// Dirname is the __dirname equivalent
func Dirname() (string, error) {
filename, err := Filename()
if err != nil {
return "", err
}
return filepath.Dir(filename), nil
}
Note that I've adjusted runtime.Caller(1) to 1 because we want to get the directory of the package that called current.Dirname(), not the directory containing the current package.
filepath.Abs("./")
Abs returns an absolute representation of path. If the path is not
absolute it will be joined with the current working directory to turn
it into an absolute path.
As stated in the comment, this returns the directory which is currently active.
os.Executable: https://tip.golang.org/pkg/os/#Executable
filepath.EvalSymlinks: https://golang.org/pkg/path/filepath/#EvalSymlinks
Full Demo:
package main
import (
"fmt"
"os"
"path/filepath"
)
func main() {
var dirAbsPath string
ex, err := os.Executable()
if err == nil {
dirAbsPath = filepath.Dir(ex)
fmt.Println(dirAbsPath)
return
}
exReal, err := filepath.EvalSymlinks(ex)
if err != nil {
panic(err)
}
dirAbsPath = filepath.Dir(exReal)
fmt.Println(dirAbsPath)
}
if you use this way :
dir, err := filepath.Abs(filepath.Dir(os.Args[0]))
if err != nil {
log.Fatal(err)
}
fmt.Println(dir)
you will get the /tmp path when you are running program using some IDE like GoLand because the executable will save and run from /tmp
i think the best way for getting the currentWorking Directory or '.' is :
import(
"os"
"fmt"
"log"
)
func main() {
dir, err := os.Getwd()
if err != nil {
log.Fatal(err)
}
fmt.Println(dir)
}
the os.Getwd() function will return the current working directory.
and its all without using of any external library :D
If you use package osext by kardianos and you need to test locally, like Derek Dowling commented:
This works fine until you'd like to use it with go run main.go for
local development. Not sure how best to get around that without
building an executable beforehand each time.
The solution to this is to make a gorun.exe utility instead of using go run. The gorun.exe utility would compile the project using "go build", then run it right after, in the normal directory of your project.
I had this issue with other compilers and found myself making these utilities since they are not shipped with the compiler... it is especially arcane with tools like C where you have to compile and link and then run it (too much work).
If anyone likes my idea of gorun.exe (or elf) I will likely upload it to github soon..
Sorry, this answer is meant as a comment, but I cannot comment due to me not having a reputation big enough yet.
Alternatively, "go run" could be modified (if it does not have this feature already) to have a parameter such as "go run -notemp" to not run the program in a temporary directory (or something similar). But I would prefer just typing out gorun or "gor" as it is shorter than a convoluted parameter. Gorun.exe or gor.exe would need to be installed in the same directory as your go compiler
Implementing gorun.exe (or gor.exe) would be trivial, as I have done it with other compilers in only a few lines of code... (famous last words ;-)
Sometimes this is enough, the first argument will always be the file path
package main
import (
"fmt"
"os"
)
func main() {
fmt.Println(os.Args[0])
// or
dir, _ := os.Getwd()
fmt.Println(dir)
}
dir, err := os.Getwd()
if err != nil {
fmt.Println(err)
}
this is for golang version: go version go1.13.7 linux/amd64
works for me, for go run main.go. If I run go build -o fileName, and put the final executable in some other folder, then that path is given while running the executable.
Do not use the "Answer recommended by Go Language" with runtime.Caller(0).
That works when you go build or go install a program, because you are re-compiling it.
But when you go build a program and then distribute it (copy) on your colleagues' workstations (who don't have Go, and just need the executable), the result of runtime.Caller(0) would still be the path of where you built it (from your computer).
Ie a path which would likely not exist on their own computer.
os.Args[0] or, better, os.Executable() (mentioned here) and kardianos/osext (mentioned here and here), are more reliable.
None of the answers here worked for me, at least on go version go1.16.2 darwin/amd64. This is the only thing close to the __dirname functionality in node
This was posted by goland engineer Daniil Maslov in the jetbrains forums
pasted below for easier reading:
The trick is actually very simple and is to get the current executing and add .. to the project root.
Create a new directory and file like testing_init.go with the following content:
package testing_init
import (
"os"
"path"
"runtime"
)
func init() {
_, filename, _, _ := runtime.Caller(0)
dir := path.Join(path.Dir(filename), "..")
err := os.Chdir(dir)
if err != nil {
panic(err)
}
}
After that, just import the package into any of the test files:
package main_test
import (
_ "project/testing_init"
)
Now you can specify paths from the project root
// GetCurrentDir
func GetCurrentDir() string {
p, _ := os.Getwd()
return p
}
// GetParentDir
func GetParentDir(dirctory string) string {
return substr(dirctory, 0, strings.LastIndex(dirctory, "/"))
}
func substr(s string, pos, length int) string {
runes := []rune(s)
l := pos + length
if l > len(runes) {
l = len(runes)
}
return string(runes[pos:l])
}
If your file is not in the main package then the above answers won't work
I tried different approaches to find find the directory of the currently running file but failed.
The best possible answer is in the question itself this is how I find the current working directory of the file which is not in the main package.
_, filename, _, _ := runtime.Caller(1)
pwd := path.Dir(filename)
Gustavo Niemeyer's answer is great.
But in Windows, runtime proc is mostly in another dir, like this:
"C:\Users\XXX\AppData\Local\Temp"
If you use relative file path, like "/config/api.yaml", this will use your project path where your code exists.

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