Go find file
last modified April 11, 2024
In this article we show how to find files with filepath.Walk.
The filepath package implements utility routines for manipulating
filename paths.
The filepath.Walk walks the file tree, calling the specified
function for each file or directory in the tree, including root. The function is
recursively walking all subdirectories.
$ go version go version go1.22.2 linux/amd64
We use Go version 1.22.2.
Go find text files
In the first example, we search for text files.
package main
import (
"fmt"
"log"
"os"
"path/filepath"
)
func main() {
var files []string
root := "/home/janbodnar/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 code example, we search for files with .txt extension.
var files []string
The matching files are stored in the files slice.
root := "/home/janbodnar/Documents"
This is the root directory where we start searching.
err := filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
The first parameter of the filepath.Walk is the root directory. The
second parameter is the walk function; the function called by
filepath.Walk to visit each each file or directory.
if err != nil {
fmt.Println(err)
return nil
}
Print the error if there is one, but continue searching elsewhere.
if !info.IsDir() && filepath.Ext(path) == ".txt" {
files = append(files, path)
}
We append the file to the files slice if the file is not a
directory and it has the .txt extension.
for _, file := range files {
fmt.Println(file)
}
Finally, we go over the files slice and print all matching files
to the console.
Go find file by size
In the next example, we find files by their size.
package main
import (
"fmt"
"log"
"os"
"path/filepath"
)
var files []string
func VisitFile(path string, info os.FileInfo, err error) error {
if err != nil {
fmt.Println(err)
return nil
}
file_size := info.Size()
if !info.IsDir() && file_size > 1024*1024 {
files = append(files, path)
}
return nil
}
func main() {
root := "/home/janbodnar/Documents"
err := filepath.Walk(root, VisitFile)
if err != nil {
log.Fatal(err)
}
for _, file := range files {
fmt.Println(file)
}
}
The example lists files that have size greater than 1 MB.
file_size := info.Size()
With the Size method, we determine the size of the file in bytes.
if !info.IsDir() && file_size > 1024*1024 {
files = append(files, path)
}
If the file is not a directory and its size is greater than 1 MB, we add the
file to the files slice.
Go find files by modification time
In the next example, we find files by modification time.
package main
import (
"fmt"
"log"
"os"
"path/filepath"
"time"
)
func FindFilesAfter(dir string, t time.Time) (files []string, err error) {
err = filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
if err != nil {
fmt.Println(err)
return nil
}
if !info.IsDir() && filepath.Ext(path) == ".txt" && info.ModTime().After(t) {
files = append(files, path)
}
return nil
})
return
}
func main() {
root := "/home/janbodnar/Documents"
t, err := time.Parse("2006-01-02T15:04:05-07:00", "2021-05-01T00:00:00+00:00")
if err != nil {
log.Fatal(err)
}
files, err := FindFilesAfter(root, t)
if err != nil {
log.Fatal(err)
}
for _, file := range files {
fmt.Println(file)
}
}
We find all text files that were modified after May 1, 2021.
if !info.IsDir() && filepath.Ext(path) == ".txt" && info.ModTime().After(t) {
files = append(files, path)
}
The ModTime gives the last modification time of the file. With the
After function, we check whether the time instant is after the
given time.
Go find file by regex pattern
In the following example, we search for file names based on a regular expression.
package main
import (
"fmt"
"log"
"os"
"path/filepath"
"regexp"
)
var files []string
func VisitFile(path string, info os.FileInfo, err error) error {
if err != nil {
fmt.Println(err)
return nil
}
if info.IsDir() || filepath.Ext(path) != ".txt" {
return nil
}
reg, err2 := regexp.Compile("^[la]")
if err2 != nil {
return err2
}
if reg.MatchString(info.Name()) {
files = append(files, path)
}
return nil
}
func main() {
err := filepath.Walk("/home/janbodnar/Documents", VisitFile)
if err != nil {
log.Fatal(err)
}
for _, file := range files {
fmt.Println(file)
}
}
In the code example, we search for text files that begin with letter l or letter a.
reg, err2 := regexp.Compile("^[la]")
We compile a regular expression with regexp.Compile.
if reg.MatchString(info.Name()) {
files = append(files, path)
}
If the regular expression matches the file name, we add the file to the
files slice.
Source
Go path/filepath package - reference
In this article we have searched files in Golang with filepath.Walk.
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