File Paths

The filepath package provides functions to parse and construct file paths in a way that is portable between operating systems; dir/file on Linux vs. dir\file on Windows, for example.

package main

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

func main() {

    // Join should be used to construct paths in a portable way.
    // It takes any number of arguments and constructs a hierarchical path from them.
    p := filepath.Join("dir1", "dir2", "filename")
    fmt.Println("p:", p)

    // You should always use Join instead of 
    // concatenating /s or \s manually.
    // In addition to providing portability
    // Join will also normalize paths by 
    // removing superfluous separators and directory changes.
    fmt.Println(filepath.Join("dir1//", "filename"))
    fmt.Println(filepath.Join("dir1/../dir1", "filename"))

    // Dir and Base can be used to split a path 
    // to the directory and the file. Alternatively
    // Split will return both in the same call.
    fmt.Println("Dir(p):", filepath.Dir(p))
    fmt.Println("Base(p):", filepath.Base(p))

    // We can check whether a path is absolute.
    fmt.Println(filepath.IsAbs("dir/file"))
    fmt.Println(filepath.IsAbs("/dir/file"))

    filename := "config.json"

    // Some file names have extensions following a dot.
    // We can split the extension out of such names with Ext.
    ext := filepath.Ext(filename)
    fmt.Println(ext)

    // To find the file’s name with the extension removed
    // use strings.TrimSuffix.
    fmt.Println(strings.TrimSuffix(filename, ext))

    // Rel finds a relative path between a base and a target.
    // It returns an error if the target cannot be made relative to base.
    rel, err := filepath.Rel("a/b", "a/b/t/file")
    if err != nil {
        panic(err)
    }
    fmt.Println(rel)

    rel, err = filepath.Rel("a/b", "a/c/t/file")
    if err != nil {
        panic(err)
    }
    fmt.Println(rel)
}

$ go run file-paths.go
p: dir1/dir2/filename
dir1/filename
dir1/filename
Dir(p): dir1/dir2
Base(p): filename
false
true
.json
config
t/file
../c/t/file