Go filepath
last modified August 24, 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.
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