I'm trying to compile a go package using exec.Command. I was successful with the arguments being "go" and "build" as such below:
package main
import (
"fmt"
"log"
"os/exec"
)
func main() {
out, err := exec.Command("go", "build").Output()
if err != nil {
log.Fatal(err)
}
fmt.Println(out)
}
However, while trying to perform a "go build" with more arguments it seems that I'm doing something wrong? This is what my code looks like:
package main
import (
"fmt"
"log"
"os/exec"
)
func main() {
out, err := exec.Command("set", "GOOS=js&&", "set", "GOARCH=wasm&&", "go", "build", "-o", "C:/Users/Daniel/Desktop/go-workspace/src/sandbox/other/wasm/assets/json.wasm", "kard").Output()
if err != nil {
log.Fatal(err)
}
fmt.Println(out)
}
The output is exec: "set": executable file not found in %PATH%
The normal command I would perform for this in the command line would be set GOOS=js&& set GOARCH=wasm&& go build -o C:\Users\Daniel\Desktop\go-workspace\src\sandbox\other\wasm\assets\json.wasm kard.
I assume there is something I'm misunderstanding with using exec.Command? I really appreciate any support.
The application uses shell syntax to set the environment variables, but the exec package does not use a shell (unless the command that you are running is a shell).
Use the command environment to specify the environment variables for the exec'ed command.
The go build does not normally write to stdout, but it does write errors to stderr. Use CombinedOutput instead of Output to easily capture error text.
cmd := exec.Command("go", "build", "-o", "C:/Users/Daniel/Desktop/go-workspace/src/sandbox/other/wasm/assets/json.wasm", "kard")
cmd.Env = []string{"GOOS=js", "GOARCH=wasm"}
out, err := cmd.CombinedOutput()
if err != nil {
fmt.Printf("%v: %s\n", err, out)
}
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)
…
}
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
I want to source shell scripts using Go. Ideally the following code
cmd := exec.Command("/bin/bash", "source", file.Name())
but, I know that "source" is a bash built-in function, not an executable.
However, I have found some ways to mimic this behavior in Python:
http://pythonwise.blogspot.fr/2010/04/sourcing-shell-script.html
Unfortunately, I don't know how to translate this in Go. Does anyone have an idea ?
Thanks !
You can set environmental variables when running a program using exec:
cmd := exec.Command("whatever")
cmd.Env = []string{"A=B"}
cmd.Run()
If you really need source then you can run your command through bash:
cmd := exec.Command("bash", "-c", "source " + file.Name() + " ; echo 'hi'")
cmd.Run()
Check out this library for a more full-featured workflow: https://github.com/progrium/go-basher.
Update: Here's an example that modifies the current environment:
package main
import (
"bufio"
"bytes"
"io/ioutil"
"log"
"os"
"os/exec"
"strings"
)
func main() {
err := ioutil.WriteFile("example_source", []byte("export FOO=bar; echo $FOO"), 0777)
if err != nil {
log.Fatal(err)
}
cmd := exec.Command("bash", "-c", "source example_source ; echo '<<<ENVIRONMENT>>>' ; env")
bs, err := cmd.CombinedOutput()
if err != nil {
log.Fatalln(err)
}
s := bufio.NewScanner(bytes.NewReader(bs))
start := false
for s.Scan() {
if s.Text() == "<<<ENVIRONMENT>>>" {
start = true
} else if start {
kv := strings.SplitN(s.Text(), "=", 2)
if len(kv) == 2 {
os.Setenv(kv[0], kv[1])
}
}
}
}
log.Println(os.Getenv("FOO"))
I have recently added such a utility function to my shell/bash Golang library:
https://godoc.org/mvdan.cc/sh/shell#SourceFile
For example, you could do:
vars, err := shell.SourceFile("foo.sh")
if err != nil { ... }
fmt.Println(vars["URL"].Value)
// http://the.url/value
It's decently safe, because it never actually calls bash nor any other program. It parses the shell script, then interprets it. But when interpreting, it has a whitelist of what files the script can open and what programs the script can execute.
The interpreter also has a context.Context, so you can set a timeout if you want to be protected against forever loops or other bad code.
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.