Go filepath

last modified January 9, 2023

Go filepath tutorial shows how to work with filename paths in Golang. The utilities are located in the path/filepath package.

The path/filepath package tries to be compatible with the target operating system-defined file paths.

$ go version
go version go1.18.1 linux/amd64

We use Go version 1.18.

Go filepath.Abs, filepath.IsAbs

An absolute path is a full path coming from the from the root directory. A relative path is defined as the path related to the present working directly.

The filepath.Abs returns an absolute representation of path. The filepath.IsAbs checks if the given path is an absolute path.

package main

import (
    "fmt"
    "log"
    "path/filepath"
)

func main() {

    fname := "./main.go"
    abs_fname, err := filepath.Abs(fname)

    if err != nil {
        log.Fatal(err)
    }

    if filepath.IsAbs(fname) {
        fmt.Printf("%s - is an absolute path\n", fname)
    } else {
        fmt.Printf("%s - is not an absolute path\n", fname)
    }

    if filepath.IsAbs(abs_fname) {
        fmt.Printf("%s - is an absolute path\n", abs_fname)
    } else {
        fmt.Printf("%s - is not an absolute path\n", abs_fname)
    }

}

The example uses both filepath.Abs and filepath.IsAbs functions.

$ go run main.go
./main.go - is not an absolute path
/home/jano/Documents/prog/go/filepath/abs/main.go - is an absolute path

Go filepath.Base, filepath.Dir

The filepath.Base function returns the last element of path and the filepath.Dir returns all but the last element of path, which is usually the file directory.

package main

import (
    "fmt"
    "log"
    "path/filepath"
)

func main() {

    p, err := filepath.Abs("./main.go")

    if err != nil {

        log.Fatal(err)
    }

    fmt.Println(p)

    fmt.Printf("Base: %s\n", filepath.Base(p))
    fmt.Printf("Dir: %s\n", filepath.Dir(p))
}

The example prints the filename and the directory name main.go file.

$ go run main.go
/home/jano/Documents/prog/go/filepath/base-dir/main.go
Base: main.go
Dir: /home/jano/Documents/prog/go/filepath/base-dir

Go filepath.Ext

The filepath.Ext returns the file name extension used by path.

package main

import (
    "fmt"
    "path/filepath"
)

func main() {

    p := "/home/user7/media/aliens.mp4"
    ext := filepath.Ext(p)
    fmt.Println("File extension:", ext)

    p = "./main.go"
    ext = filepath.Ext(p)
    fmt.Println("File extension:", ext)
}

The example returns file extensions of two paths.

$ go run main.go
File extension: .mp4
File extension: .go

Go filepath.Clean

The filepath.Clean function cleans the filepaths from duplications and irregularities.

package main

import (
    "fmt"
    "path"
)

func main() {

    paths := []string{
        "home/user7",
        "home//user7",
        "home/user7/.",
        "home/user7/Documents/..",
        "/../home/user7",
        "/../home/Documents/../././/user7",
        "",
    }

    for _, p := range paths {
        fmt.Printf("%q = %q\n", p, path.Clean(p))
    }
}

In the example, we clean a few filepaths.

$ go run main.go
"home/user7" = "home/user7"
"home//user7" = "home/user7"
"home/user7/." = "home/user7"
"home/user7/Documents/.." = "home/user7"
"/../home/user7" = "/home/user7"
"/../home/Documents/../././/user7" = "/home/user7"
"" = "."

Go filepath.Split, filepath.SplitList

The filepath.Split function splits the given path into a directory and file name component. The filepath.SplitList function splits a list of paths joined by the OS-specific line separator.

package main

import (
    "fmt"
    "log"
    "os"
    "path/filepath"
)

func main() {

    cwd, err := os.Getwd()

    if err != nil {
        log.Fatal(err)
    }

    dir, file := filepath.Split(cwd)

    fmt.Printf("Directory: %s\n", dir)
    fmt.Printf("File: %s\n", file)

    home, err := os.UserHomeDir()

    if err != nil {
        log.Fatal(err)
    }

    fmt.Println("-------------------------")

    dir, file = filepath.Split(home)

    fmt.Printf("Directory: %s\n", dir)
    fmt.Printf("File: %s\n", file)

    path_env := os.Getenv("PATH")
    paths := filepath.SplitList(path_env)

    for _, p := range paths {
        fmt.Println(p)
    }
}

In the example, we first split the current working directory and the user home directory. Then we split the list of paths inside the PATH variable.

Go filepath.Walk

The filepath.Walk function walks the file tree rooted at root.

func Walk(root string, fn WalkFunc) error

It calls the WalkFunc for each file or directory in the tree, including root.

package main

import (
    "fmt"
    "log"
    "os"
    "path/filepath"
)

func main() {

    var files []string

    root := "/home/jano/Documents"

    err := filepath.Walk(root, func(path string, info os.FileInfo, err error) error {

        if err != nil {

            fmt.Println(err)
            return nil
        }

        if !info.IsDir() && filepath.Ext(path) == ".txt" {
            files = append(files, path)
        }

        return nil
    })

    if err != nil {
        log.Fatal(err)
    }

    for _, file := range files {
        fmt.Println(file)
    }
}

In the example, we go through the files inside the Documents directory and list all text files (files having .txt extension).

Go filepath.Glob

The filepath.Glob returns the names of all files matching pattern or nil if there is no matching file.

func Glob(pattern string) (matches []string, err error)

This is the syntax of the filepath.Glob function.

package main

import (
    "fmt"
    "log"
    "path/filepath"
)

func main() {

    files, err := filepath.Glob("/home/jano/Documents/prog/go/**/**/*.go")

    fmt.Println(len(files))

    if err != nil {
        log.Fatal(err)
    }

    for _, file := range files {

        fmt.Println(file)
    }
}

The example lists all Go files in the given directory. With the ** pattern, the listing is recursive.

Go filepath.VolumeName

The filepath.VolumeName function returns leading volume name on Windows. On other platforms, it returns an empty string.

package main

import (
    "fmt"
    "log"
    "path/filepath"
)

func main() {

    fname := "./main.go"
    ap, err := filepath.Abs(fname)

    if err != nil {

        log.Fatal(err)
    }

    fmt.Println(filepath.VolumeName(ap))
}

The example prints the volume name of the main.go file.

$ go run main.go
C:

In this article, we have worked filename paths in Go utilizing the filename/path package.

List all Go tutorials.