Related
I am currently in the process of creating a little Go App. Right now I am working on the DB part. The Library I use is this one: https://github.com/jackc/pgx
The problem I have is that every time I try to execute the database read, it tells me that my 'conn is busy'. I read about using a pgxpool instead of a single connection, but it still does not work. What am I doing wrong?
func (postgre *PostgreClient) read(query string) (pgx.Row, error) {
client, err := postgre.client.Acquire(context.TODO())
transaction, err := client.BeginTx(context.TODO(), pgx.TxOptions{})
if err != nil {
return nil, err
}
defer transaction.Rollback(context.TODO())
rows := transaction.QueryRow(context.TODO(), query)
if err != nil {
return nil, err
}
err = transaction.Commit(context.TODO())
return rows, err
}
Thanks in advance.
You have to scan the row before you commit the transaction.
If you want the handling of the transaction to remain within the function you can pass an interface that does the scanning also inside the function.
For example:
// implemented by *sql.Row & *sql.Rows
type Row interface {
Scan(dst ...interface{}) error
}
// implemented by your "models"
type RowScanner interface {
ScanRow(r Row) error
}
type User struct {
Id int
Email string
}
func (u *User) ScanRow(r Row) error {
return r.Scan(
&u.Id,
&u.Email,
)
}
func (postgre *PostgreClient) read(query string, rs RowScanner) (err error) {
conn, err := postgre.client.Acquire(context.TODO())
if err != nil {
return err
}
defer conn.Release()
tx, err := conn.BeginTx(context.TODO(), pgx.TxOptions{})
if err != nil {
return err
}
defer func() {
if err != nil {
tx.Rollback(context.TODO())
} else {
tx.Commit(context.TODO())
}
}()
row := tx.QueryRow(context.TODO(), query)
if err != nil {
return nil, err
}
return rs.ScanRow(row)
}
u := new(User)
if err := pg.read("select id, email from users limit 1", u); err != nil {
panic(err)
}
For scanning a list of models:
type UserList []*User
func (ul *UserList) ScanRow(r Row) error {
u := new(User)
if err := u.ScanRow(r); err != nil {
return err
}
*ul = append(*ul, u)
return nil
}
func (postgre *PostgreClient) list(query string, rs RowScanner) (err error) {
conn, err := postgre.client.Acquire(context.TODO())
if err != nil {
return err
}
defer conn.Release()
tx, err := conn.BeginTx(context.TODO(), pgx.TxOptions{})
if err != nil {
return err
}
defer func() {
if err != nil {
tx.Rollback(context.TODO())
} else {
tx.Commit(context.TODO())
}
}()
rows, err := tx.Query(context.TODO(), query)
if err != nil {
return err
}
defer rows.Close()
for rows.Next() {
if err := rs.ScanRow(rows); err != nil {
return err
}
}
return rows.Err()
}
ul := new(UserList)
if err := pg.list("select id, email from users", ul); err != nil {
panic(err)
}
I'm trying to find an element on the page, but it doesn't work out what could be the reason?
package main
import (
"github.com/tebeka/selenium"
"log"
"time"
)
func main() {
caps := selenium.Capabilities{
"browserName": "chrome",
}
wd, err := selenium.NewRemote(caps, "http://localhost:4444/wd/hub")
if err != nil{
log.Fatal(err)
}
defer func() {
if err := wd.Quit(); err != nil {
log.Fatal(err)
}
}()
if err := wd.SetPageLoadTimeout(time.Second * 10); err != nil {
log.Fatal(err)
}
if err = wd.SetImplicitWaitTimeout(time.Second * 10); err != nil {
log.Fatal(err)
}
if err = wd.Get("https://www.facebook.com/ads/library/?active_status=all&ad_type=political_and_issue_ads&country=ALL&sort_data[direction]=desc&sort_data[mode]=relevancy_monthly_grouped"); err != nil {
log.Fatal(err)
}
title, err := wd.Title()
if err != nil {
log.Fatalln(err)
}
log.Println(title)
elem, err := wd.FindElement(selenium.ByXPATH, "//*[#id=\"content\"]/div/div/div[3]/div/div[4]/div")
if err != nil {
log.Fatal(err)
}
log.Println(elem.Text())
}
gives an error message:
no such element: no such element: Unable to locate element: {"method":"xpath","selector":"//*[#id="content"]/div/div/div[3]/div/div[4]/div"}
The hub was raised in docker. Image https://hub.docker.com/r/selenium/standalone-chrome
Just try to not use XPATHs with Selenium if you can.
Search for it using .ByTag and look for a unique property of your element to find it. Never rely on XPATHs, classes or even IDs for famous websites since they often change.
Check my answer here: How to click on the Ask to join button within https://meet.google.com using Selenium and Python?
I'm trying to run multiple commands through ssh but seems that Session.Run allows only one command per session ( unless I'm wrong). I'm wondering how can I bypass this limitation and reuse the session or send a sequence of commands.
The reason is that I need to run sudo su within the same session with the next command ( sh /usr/bin/myscript.sh )
Session.Shell allows for more than one command to be run, by passing your commands in via session.StdinPipe().
Be aware that using this approach will make your life more complicated; instead of having a one-shot function call that runs the command and collects the output once it's complete, you'll need to manage your input buffer (don't forget a \n at the end of a command), wait for output to actually come back from the SSH server, then deal with that output appropriately (if you had multiple commands in flight and want to know what output belongs to what input, you'll need to have a plan to figure that out).
stdinBuf, _ := session.StdinPipe()
err := session.Shell()
stdinBuf.Write([]byte("cd /\n"))
// The command has been sent to the device, but you haven't gotten output back yet.
// Not that you can't send more commands immediately.
stdinBuf.Write([]byte("ls\n"))
// Then you'll want to wait for the response, and watch the stdout buffer for output.
While for your specific problem, you can easily run sudo /path/to/script.sh, it shock me that there wasn't a simple way to run multiple commands on the same session, so I came up with a bit of a hack, YMMV:
func MuxShell(w io.Writer, r io.Reader) (chan<- string, <-chan string) {
in := make(chan string, 1)
out := make(chan string, 1)
var wg sync.WaitGroup
wg.Add(1) //for the shell itself
go func() {
for cmd := range in {
wg.Add(1)
w.Write([]byte(cmd + "\n"))
wg.Wait()
}
}()
go func() {
var (
buf [65 * 1024]byte
t int
)
for {
n, err := r.Read(buf[t:])
if err != nil {
close(in)
close(out)
return
}
t += n
if buf[t-2] == '$' { //assuming the $PS1 == 'sh-4.3$ '
out <- string(buf[:t])
t = 0
wg.Done()
}
}
}()
return in, out
}
func main() {
config := &ssh.ClientConfig{
User: "kf5",
Auth: []ssh.AuthMethod{
ssh.Password("kf5"),
},
}
client, err := ssh.Dial("tcp", "127.0.0.1:22", config)
if err != nil {
panic(err)
}
defer client.Close()
session, err := client.NewSession()
if err != nil {
log.Fatalf("unable to create session: %s", err)
}
defer session.Close()
modes := ssh.TerminalModes{
ssh.ECHO: 0, // disable echoing
ssh.TTY_OP_ISPEED: 14400, // input speed = 14.4kbaud
ssh.TTY_OP_OSPEED: 14400, // output speed = 14.4kbaud
}
if err := session.RequestPty("xterm", 80, 40, modes); err != nil {
log.Fatal(err)
}
w, err := session.StdinPipe()
if err != nil {
panic(err)
}
r, err := session.StdoutPipe()
if err != nil {
panic(err)
}
in, out := MuxShell(w, r)
if err := session.Start("/bin/sh"); err != nil {
log.Fatal(err)
}
<-out //ignore the shell output
in <- "ls -lhav"
fmt.Printf("ls output: %s\n", <-out)
in <- "whoami"
fmt.Printf("whoami: %s\n", <-out)
in <- "exit"
session.Wait()
}
If your shell prompt doesn't end with $ ($ followed by a space), this will deadlock, hence why it's a hack.
NewSession is a method of a connection. You don't need to create a new connection each time. A Session seems to be what this library calls a channel for the client, and many channels are multiplexed in a single connection. Hence:
func executeCmd(cmd []string, hostname string, config *ssh.ClientConfig) string {
conn, err := ssh.Dial("tcp", hostname+":8022", config)
if err != nil {
log.Fatal(err)
}
defer conn.Close()
var stdoutBuf bytes.Buffer
for _, command := range cmd {
session, err := conn.NewSession()
if err != nil {
log.Fatal(err)
}
defer session.Close()
session.Stdout = &stdoutBuf
session.Run(command)
}
return hostname + ": " + stdoutBuf.String()
}
So you open a new session(channel) and you run command within the existing ssh connection but with a new session(channel) each time.
You can use a small trick: sh -c 'cmd1&&cmd2&&cmd3&&cmd4&&etc..'
This is a single command, the actual commands are passed as argument to the shell which will execute them. This is how Docker handles multiple commands.
This works for me.
package main
import (
"fmt"
"golang.org/x/crypto/ssh"
// "io"
"log"
"os"
// Uncomment to store output in variable
//"bytes"
)
type MachineDetails struct {
username, password, hostname, port string
}
func main() {
h1 := MachineDetails{"root", "xxxxx", "x.x.x.x", "22"}
// Uncomment to store output in variable
//var b bytes.Buffer
//sess.Stdout = &b
//sess.Stderr = &b
commands := []string{
"pwd",
"whoami",
"echo 'bye'",
"exit",
}
connectHost(h1, commands)
// Uncomment to store in variable
//fmt.Println(b.String())
}
func connectHost(hostParams MachineDetails, commands []string) {
// SSH client config
config := &ssh.ClientConfig{
User: hostParams.username,
Auth: []ssh.AuthMethod{
ssh.Password(hostParams.password),
},
// Non-production only
HostKeyCallback: ssh.InsecureIgnoreHostKey(),
}
// Connect to host
client, err := ssh.Dial("tcp", hostParams.hostname+":"+hostParams.port, config)
if err != nil {
log.Fatal(err)
}
defer client.Close()
// Create sesssion
sess, err := client.NewSession()
if err != nil {
log.Fatal("Failed to create session: ", err)
}
defer sess.Close()
// Enable system stdout
// Comment these if you uncomment to store in variable
sess.Stdout = os.Stdout
sess.Stderr = os.Stderr
// StdinPipe for commands
stdin, err := sess.StdinPipe()
if err != nil {
log.Fatal(err)
}
// Start remote shell
err = sess.Shell()
if err != nil {
log.Fatal(err)
}
// send the commands
for _, cmd := range commands {
_, err = fmt.Fprintf(stdin, "%s\n", cmd)
if err != nil {
log.Fatal(err)
}
}
// Wait for sess to finish
err = sess.Wait()
if err != nil {
log.Fatal(err)
}
// return sess, stdin, err
}
func createSession() {
}
Really liked OneOfOne's answer which inspired me with a more generalized solution to taken a variable that could match the tail of the read bytes and break the blocking read (also no need to fork two extra threads for blocking read and writes). The known limitation is (as in the original solution) if the matching string comes after 64 * 1024 bytes, then this code will spin forever.
package main
import (
"fmt"
"golang.org/x/crypto/ssh"
"io"
"log"
)
var escapePrompt = []byte{'$', ' '}
func main() {
config := &ssh.ClientConfig{
User: "dummy",
Auth: []ssh.AuthMethod{
ssh.Password("dummy"),
},
HostKeyCallback: ssh.InsecureIgnoreHostKey(),
}
client, err := ssh.Dial("tcp", "127.0.0.1:22", config)
if err != nil {
panic(err)
}
defer client.Close()
session, err := client.NewSession()
if err != nil {
log.Fatalf("unable to create session: %s", err)
}
defer session.Close()
modes := ssh.TerminalModes{
ssh.ECHO: 0, // disable echoing
ssh.TTY_OP_ISPEED: 14400, // input speed = 14.4kbaud
ssh.TTY_OP_OSPEED: 14400, // output speed = 14.4kbaud
}
if err := session.RequestPty("xterm", 80, 40, modes); err != nil {
log.Fatal(err)
}
w, err := session.StdinPipe()
if err != nil {
panic(err)
}
r, err := session.StdoutPipe()
if err != nil {
panic(err)
}
if err := session.Start("/bin/sh"); err != nil {
log.Fatal(err)
}
readUntil(r, escapePrompt) //ignore the shell output
write(w, "ls -lhav")
out, err := readUntil(r, escapePrompt)
fmt.Printf("ls output: %s\n", *out)
write(w, "whoami")
out, err = readUntil(r, escapePrompt)
fmt.Printf("whoami: %s\n", *out)
write(w, "exit")
session.Wait()
}
func write(w io.WriteCloser, command string) error {
_, err := w.Write([]byte(command + "\n"))
return err
}
func readUntil(r io.Reader, matchingByte []byte) (*string, error) {
var buf [64 * 1024]byte
var t int
for {
n, err := r.Read(buf[t:])
if err != nil {
return nil, err
}
t += n
if isMatch(buf[:t], t, matchingByte) {
stringResult := string(buf[:t])
return &stringResult, nil
}
}
}
func isMatch(bytes []byte, t int, matchingBytes []byte) bool {
if t >= len(matchingBytes) {
for i := 0; i < len(matchingBytes); i++ {
if bytes[t - len(matchingBytes) + i] != matchingBytes[i] {
return false
}
}
return true
}
return false
}
get inspiration from this
i spent several days and that answer inspires me to try about using sdtin to run multiple commands, finally succeed. and i want to say i dont know golang at all , hence it may be redundant ,but the code works.
if _, err := w.Write([]byte("sys\r")); err != nil {
panic("Failed to run: " + err.Error())
}
if _, err := w.Write([]byte("wlan\r")); err != nil {
panic("Failed to run: " + err.Error())
}
if _, err := w.Write([]byte("ap-id 2099\r")); err != nil {
panic("Failed to run: " + err.Error())
}
if _, err := w.Write([]byte("ap-group xuebao-free\r")); err != nil {
panic("Failed to run: " + err.Error())
}
if _, err := w.Write([]byte("y\r")); err != nil {
panic("Failed to run: " + err.Error())
}
its function is the same asterminal operation
here is the whole code:
/* switch ssh
*/
package main
import (
"flag"
"fmt"
"io"
"log"
"net"
"os"
"strings"
"sync"
)
import (
"golang.org/x/crypto/ssh"
)
func main() {
//go run ./testConfig.go --username="aaa" --passwd='aaa' --ip_port="192.168.6.87" --cmd='display version'
username := flag.String("username", "aaa", "username")
passwd := flag.String("passwd", "aaa", "password")
ip_port := flag.String("ip_port", "1.1.1.1:22", "ip and port")
cmdstring := flag.String("cmd", "display arp statistics all", "cmdstring")
flag.Parse()
fmt.Println("username:", *username)
fmt.Println("passwd:", *passwd)
fmt.Println("ip_port:", *ip_port)
fmt.Println("cmdstring:", *cmdstring)
config := &ssh.ClientConfig{
User: *username,
Auth: []ssh.AuthMethod{
ssh.Password(*passwd),
},
Config: ssh.Config{
Ciphers: []string{"aes128-cbc", "aes128-ctr"},
},
HostKeyCallback: func(hostname string, remote net.Addr, key ssh.PublicKey) error {
return nil
},
}
// config.Config.Ciphers = append(config.Config.Ciphers, "aes128-cbc")
clinet, err := ssh.Dial("tcp", *ip_port, config)
checkError(err, "connet "+*ip_port)
session, err := clinet.NewSession()
defer session.Close()
checkError(err, "creae shell")
modes := ssh.TerminalModes{
ssh.ECHO: 1, // disable echoing
ssh.TTY_OP_ISPEED: 14400, // input speed = 14.4kbaud
ssh.TTY_OP_OSPEED: 14400, // output speed = 14.4kbaud
}
if err := session.RequestPty("vt100", 80, 40, modes); err != nil {
log.Fatal(err)
}
w, err := session.StdinPipe()
if err != nil {
panic(err)
}
r, err := session.StdoutPipe()
if err != nil {
panic(err)
}
e, err := session.StderrPipe()
if err != nil {
panic(err)
}
in, out := MuxShell(w, r, e)
if err := session.Shell(); err != nil {
log.Fatal(err)
}
<-out //ignore the shell output
in <- *cmdstring
fmt.Printf("%s\n", <-out)
if _, err := w.Write([]byte("sys\r")); err != nil {
panic("Failed to run: " + err.Error())
}
if _, err := w.Write([]byte("wlan\r")); err != nil {
panic("Failed to run: " + err.Error())
}
if _, err := w.Write([]byte("ap-id 2099\r")); err != nil {
panic("Failed to run: " + err.Error())
}
if _, err := w.Write([]byte("ap-group xuebao-free\r")); err != nil {
panic("Failed to run: " + err.Error())
}
if _, err := w.Write([]byte("y\r")); err != nil {
panic("Failed to run: " + err.Error())
}
in <- "quit"
_ = <-out
session.Wait()
}
func checkError(err error, info string) {
if err != nil {
fmt.Printf("%s. error: %s\n", info, err)
os.Exit(1)
}
}
func MuxShell(w io.Writer, r, e io.Reader) (chan<- string, <-chan string) {
in := make(chan string, 5)
out := make(chan string, 5)
var wg sync.WaitGroup
wg.Add(1) //for the shell itself
go func() {
for cmd := range in {
wg.Add(1)
w.Write([]byte(cmd + "\n"))
wg.Wait()
}
}()
go func() {
var (
buf [1024 * 1024]byte
t int
)
for {
n, err := r.Read(buf[t:])
if err != nil {
fmt.Println(err.Error())
close(in)
close(out)
return
}
t += n
result := string(buf[:t])
if strings.Contains(string(buf[t-n:t]), "More") {
w.Write([]byte("\n"))
}
if strings.Contains(result, "username:") ||
strings.Contains(result, "password:") ||
strings.Contains(result, ">") {
out <- string(buf[:t])
t = 0
wg.Done()
}
}
}()
return in, out
}
The following code works for me.
func main() {
key, err := ioutil.ReadFile("path to your key file")
if err != nil {
panic(err)
}
signer, err := ssh.ParsePrivateKey([]byte(key))
if err != nil {
panic(err)
}
config := &ssh.ClientConfig{
User: "ubuntu",
Auth: []ssh.AuthMethod{
ssh.PublicKeys(signer),
},
}
client, err := ssh.Dial("tcp", "52.91.35.179:22", config)
if err != nil {
panic(err)
}
session, err := client.NewSession()
if err != nil {
panic(err)
}
defer session.Close()
session.Stdout = os.Stdout
session.Stderr = os.Stderr
session.Stdin = os.Stdin
session.Shell()
session.Wait()
}
I'm trying to upload images from my computer to a website using go. Usually, I use a bash script that sends a file and a key to the server:
curl -F "image"=#"IMAGEFILE" -F "key"="KEY" URL
it works fine, but I'm trying to convert this request into my golang program.
http://matt.aimonetti.net/posts/2013/07/01/golang-multipart-file-upload-example/
I tried this link and many others, but, for each code that I try, the response from the server is "no image sent", and I've no idea why. If someone knows what's happening with the example above.
Here's some sample code.
In short, you'll need to use the mime/multipart package to build the form.
package main
import (
"bytes"
"fmt"
"io"
"mime/multipart"
"net/http"
"net/http/httptest"
"net/http/httputil"
"os"
"strings"
)
func main() {
var client *http.Client
var remoteURL string
{
//setup a mocked http client.
ts := httptest.NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
b, err := httputil.DumpRequest(r, true)
if err != nil {
panic(err)
}
fmt.Printf("%s", b)
}))
defer ts.Close()
client = ts.Client()
remoteURL = ts.URL
}
//prepare the reader instances to encode
values := map[string]io.Reader{
"file": mustOpen("main.go"), // lets assume its this file
"other": strings.NewReader("hello world!"),
}
err := Upload(client, remoteURL, values)
if err != nil {
panic(err)
}
}
func Upload(client *http.Client, url string, values map[string]io.Reader) (err error) {
// Prepare a form that you will submit to that URL.
var b bytes.Buffer
w := multipart.NewWriter(&b)
for key, r := range values {
var fw io.Writer
if x, ok := r.(io.Closer); ok {
defer x.Close()
}
// Add an image file
if x, ok := r.(*os.File); ok {
if fw, err = w.CreateFormFile(key, x.Name()); err != nil {
return
}
} else {
// Add other fields
if fw, err = w.CreateFormField(key); err != nil {
return
}
}
if _, err = io.Copy(fw, r); err != nil {
return err
}
}
// Don't forget to close the multipart writer.
// If you don't close it, your request will be missing the terminating boundary.
w.Close()
// Now that you have a form, you can submit it to your handler.
req, err := http.NewRequest("POST", url, &b)
if err != nil {
return
}
// Don't forget to set the content type, this will contain the boundary.
req.Header.Set("Content-Type", w.FormDataContentType())
// Submit the request
res, err := client.Do(req)
if err != nil {
return
}
// Check the response
if res.StatusCode != http.StatusOK {
err = fmt.Errorf("bad status: %s", res.Status)
}
return
}
func mustOpen(f string) *os.File {
r, err := os.Open(f)
if err != nil {
panic(err)
}
return r
}
Here's a function I've used that uses io.Pipe() to avoid reading in the entire file to memory or needing to manage any buffers. It handles only a single file, but could easily be extended to handle more by adding more parts within the goroutine. The happy path works well. The error paths have not hand much testing.
import (
"fmt"
"io"
"mime/multipart"
"net/http"
"os"
)
func UploadMultipartFile(client *http.Client, uri, key, path string) (*http.Response, error) {
body, writer := io.Pipe()
req, err := http.NewRequest(http.MethodPost, uri, body)
if err != nil {
return nil, err
}
mwriter := multipart.NewWriter(writer)
req.Header.Add("Content-Type", mwriter.FormDataContentType())
errchan := make(chan error)
go func() {
defer close(errchan)
defer writer.Close()
defer mwriter.Close()
w, err := mwriter.CreateFormFile(key, path)
if err != nil {
errchan <- err
return
}
in, err := os.Open(path)
if err != nil {
errchan <- err
return
}
defer in.Close()
if written, err := io.Copy(w, in); err != nil {
errchan <- fmt.Errorf("error copying %s (%d bytes written): %v", path, written, err)
return
}
if err := mwriter.Close(); err != nil {
errchan <- err
return
}
}()
resp, err := client.Do(req)
merr := <-errchan
if err != nil || merr != nil {
return resp, fmt.Errorf("http error: %v, multipart error: %v", err, merr)
}
return resp, nil
}
After having to decode the accepted answer for this question for use in my unit testing I finally ended up with the follow refactored code:
func createMultipartFormData(t *testing.T, fieldName, fileName string) (bytes.Buffer, *multipart.Writer) {
var b bytes.Buffer
var err error
w := multipart.NewWriter(&b)
var fw io.Writer
file := mustOpen(fileName)
if fw, err = w.CreateFormFile(fieldName, file.Name()); err != nil {
t.Errorf("Error creating writer: %v", err)
}
if _, err = io.Copy(fw, file); err != nil {
t.Errorf("Error with io.Copy: %v", err)
}
w.Close()
return b, w
}
func mustOpen(f string) *os.File {
r, err := os.Open(f)
if err != nil {
pwd, _ := os.Getwd()
fmt.Println("PWD: ", pwd)
panic(err)
}
return r
}
Now it should be pretty easy to use:
b, w := createMultipartFormData(t, "image","../luke.png")
req, err := http.NewRequest("POST", url, &b)
if err != nil {
return
}
// Don't forget to set the content type, this will contain the boundary.
req.Header.Set("Content-Type", w.FormDataContentType())
Here is an option that works for files or strings:
package main
import (
"bytes"
"io"
"mime/multipart"
"os"
"strings"
)
func createForm(form map[string]string) (string, io.Reader, error) {
body := new(bytes.Buffer)
mp := multipart.NewWriter(body)
defer mp.Close()
for key, val := range form {
if strings.HasPrefix(val, "#") {
val = val[1:]
file, err := os.Open(val)
if err != nil { return "", nil, err }
defer file.Close()
part, err := mp.CreateFormFile(key, val)
if err != nil { return "", nil, err }
io.Copy(part, file)
} else {
mp.WriteField(key, val)
}
}
return mp.FormDataContentType(), body, nil
}
Example:
package main
import "net/http"
func main() {
form := map[string]string{"image": "#IMAGEFILE", "key": "KEY"}
ct, body, err := createForm(form)
if err != nil {
panic(err)
}
http.Post("https://stackoverflow.com", ct, body)
}
https://golang.org/pkg/mime/multipart#Writer.WriteField
Send file from one service to another:
func UploadFile(network, uri string, f multipart.File, h *multipart.FileHeader) error {
buf := new(bytes.Buffer)
writer := multipart.NewWriter(buf)
part, err := writer.CreateFormFile("file", h.Filename)
if err != nil {
log.Println(err)
return err
}
b, err := ioutil.ReadAll(f)
if err != nil {
log.Println(err)
return err
}
part.Write(b)
writer.Close()
req, _ := http.NewRequest("POST", uri, buf)
req.Header.Add("Content-Type", writer.FormDataContentType())
client := &http.Client{}
resp, err := client.Do(req)
if err != nil {
return err
}
defer resp.Body.Close()
b, _ = ioutil.ReadAll(resp.Body)
if resp.StatusCode >= 400 {
return errors.New(string(b))
}
return nil
}
To extend on #attila-o answer, here is the code I went with to perform a POST HTTP req in Go with:
1 file
configurable file name (f.Name() didn't work)
extra form fields.
Curl representation:
curl -X POST \
http://localhost:9091/storage/add \
-H 'content-type: multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW' \
-F owner=0xc916Cfe5c83dD4FC3c3B0Bf2ec2d4e401782875e \
-F password=$PWD \
-F file=#./internal/file_example_JPG_500kB.jpg
Go way:
client := &http.Client{
Timeout: time.Second * 10,
}
req, err := createStoragePostReq(cfg)
res, err := executeStoragePostReq(client, req)
func createStoragePostReq(cfg Config) (*http.Request, error) {
extraFields := map[string]string{
"owner": "0xc916cfe5c83dd4fc3c3b0bf2ec2d4e401782875e",
"password": "pwd",
}
url := fmt.Sprintf("http://localhost:%d%s", cfg.HttpServerConfig().Port(), lethstorage.AddRoute)
b, w, err := createMultipartFormData("file","./internal/file_example_JPG_500kB.jpg", "file_example_JPG_500kB.jpg", extraFields)
if err != nil {
return nil, err
}
req, err := http.NewRequest("POST", url, &b)
if err != nil {
return nil, err
}
req.Header.Set("Content-Type", w.FormDataContentType())
return req, nil
}
func executeStoragePostReq(client *http.Client, req *http.Request) (lethstorage.AddRes, error) {
var addRes lethstorage.AddRes
res, err := client.Do(req)
if err != nil {
return addRes, err
}
defer res.Body.Close()
data, err := ioutil.ReadAll(res.Body)
if err != nil {
return addRes, err
}
err = json.Unmarshal(data, &addRes)
if err != nil {
return addRes, err
}
return addRes, nil
}
func createMultipartFormData(fileFieldName, filePath string, fileName string, extraFormFields map[string]string) (b bytes.Buffer, w *multipart.Writer, err error) {
w = multipart.NewWriter(&b)
var fw io.Writer
file, err := os.Open(filePath)
if fw, err = w.CreateFormFile(fileFieldName, fileName); err != nil {
return
}
if _, err = io.Copy(fw, file); err != nil {
return
}
for k, v := range extraFormFields {
w.WriteField(k, v)
}
w.Close()
return
}
I have found this tutorial very helpful to clarify my confusions about file uploading in Go.
Basically you upload the file via ajax using form-data on a client and use the following small snippet of Go code on the server:
file, handler, err := r.FormFile("img") // img is the key of the form-data
if err != nil {
fmt.Println(err)
return
}
defer file.Close()
fmt.Println("File is good")
fmt.Println(handler.Filename)
fmt.Println()
fmt.Println(handler.Header)
f, err := os.OpenFile(handler.Filename, os.O_WRONLY|os.O_CREATE, 0666)
if err != nil {
fmt.Println(err)
return
}
defer f.Close()
io.Copy(f, file)
Here r is *http.Request. P.S. this just stores the file in the same folder and does not perform any security checks.
I'm new to Go, and can't figure out how to use the compress/gzip package to my advantage. Basically, I just want to write something to a file, gzip it and read it directly from the zipped format through another script. I would really appreciate if someone could give me an example on how to do this.
All the compress packages implement the same interface. You would use something like this to compress:
var b bytes.Buffer
w := gzip.NewWriter(&b)
w.Write([]byte("hello, world\n"))
w.Close()
And this to unpack:
r, err := gzip.NewReader(&b)
io.Copy(os.Stdout, r)
r.Close()
Pretty much the same answer as Laurent, but with the file io:
import (
"bytes"
"compress/gzip"
"io/ioutil"
)
// ...
var b bytes.Buffer
w := gzip.NewWriter(&b)
w.Write([]byte("hello, world\n"))
w.Close() // You must close this first to flush the bytes to the buffer.
err := ioutil.WriteFile("hello_world.txt.gz", b.Bytes(), 0666)
For the Read part, something like the useful ioutil.ReadFile for .gz files could be :
func ReadGzFile(filename string) ([]byte, error) {
fi, err := os.Open(filename)
if err != nil {
return nil, err
}
defer fi.Close()
fz, err := gzip.NewReader(fi)
if err != nil {
return nil, err
}
defer fz.Close()
s, err := ioutil.ReadAll(fz)
if err != nil {
return nil, err
}
return s, nil
}
Here the func for unpack gzip file to destination file:
func UnpackGzipFile(gzFilePath, dstFilePath string) (int64, error) {
gzFile, err := os.Open(gzFilePath)
if err != nil {
return 0, fmt.Errorf("open file %q to unpack: %w", gzFilePath, err)
}
dstFile, err := os.OpenFile(dstFilePath, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0660)
if err != nil {
return 0, fmt.Errorf("create destination file %q to unpack: %w", dstFilePath, err)
}
defer dstFile.Close()
ioReader, ioWriter := io.Pipe()
defer ioReader.Close()
go func() { // goroutine leak is possible here
gzReader, _ := gzip.NewReader(gzFile)
// it is important to close the writer or reading from the other end of the
// pipe or io.copy() will never finish
defer func(){
gzFile.Close()
gzReader.Close()
ioWriter.Close()
}()
io.Copy(ioWriter, gzReader)
}()
written, err := io.Copy(dstFile, ioReader)
if err != nil {
return 0, err // goroutine leak is possible here
}
return written, nil
}
I decided to combine ideas from others answers and just provide a full example program. Obviously there are many different ways to do the same thing. This is just one way:
package main
import (
"compress/gzip"
"fmt"
"io/ioutil"
"os"
)
var zipFile = "zipfile.gz"
func main() {
writeZip()
readZip()
}
func writeZip() {
handle, err := openFile(zipFile)
if err != nil {
fmt.Println("[ERROR] Opening file:", err)
}
zipWriter, err := gzip.NewWriterLevel(handle, 9)
if err != nil {
fmt.Println("[ERROR] New gzip writer:", err)
}
numberOfBytesWritten, err := zipWriter.Write([]byte("Hello, World!\n"))
if err != nil {
fmt.Println("[ERROR] Writing:", err)
}
err = zipWriter.Close()
if err != nil {
fmt.Println("[ERROR] Closing zip writer:", err)
}
fmt.Println("[INFO] Number of bytes written:", numberOfBytesWritten)
closeFile(handle)
}
func readZip() {
handle, err := openFile(zipFile)
if err != nil {
fmt.Println("[ERROR] Opening file:", err)
}
zipReader, err := gzip.NewReader(handle)
if err != nil {
fmt.Println("[ERROR] New gzip reader:", err)
}
defer zipReader.Close()
fileContents, err := ioutil.ReadAll(zipReader)
if err != nil {
fmt.Println("[ERROR] ReadAll:", err)
}
fmt.Printf("[INFO] Uncompressed contents: %s\n", fileContents)
// ** Another way of reading the file **
//
// fileInfo, _ := handle.Stat()
// fileContents := make([]byte, fileInfo.Size())
// bytesRead, err := zipReader.Read(fileContents)
// if err != nil {
// fmt.Println("[ERROR] Reading gzip file:", err)
// }
// fmt.Println("[INFO] Number of bytes read from the file:", bytesRead)
closeFile(handle)
}
func openFile(fileToOpen string) (*os.File, error) {
return os.OpenFile(fileToOpen, openFileOptions, openFilePermissions)
}
func closeFile(handle *os.File) {
if handle == nil {
return
}
err := handle.Close()
if err != nil {
fmt.Println("[ERROR] Closing file:", err)
}
}
const openFileOptions int = os.O_CREATE | os.O_RDWR
const openFilePermissions os.FileMode = 0660
Having a full example like this should be helpful for future reference.
To compress any Go object of interface type as input
func compress(obj interface{}) ([]byte, error) {
var b bytes.Buffer
objBytes, err := json.Marshal(obj)
if err != nil {
return nil, err
}
gz := gzip.NewWriter(&b)
defer gz.Close() //NOT SUFFICIENT, DON'T DEFER WRITER OBJECTS
if _, err := gz.Write(objBytes); err != nil {
return nil, err
}
// NEED TO CLOSE EXPLICITLY
if err := gz.Close(); err != nil {
return nil, err
}
return b.Bytes(), nil
}
To decompress the same,
func decompress(obj []byte) ([]byte, error) {
r, err := gzip.NewReader(bytes.NewReader(obj))
if err != nil {
return nil, err
}
defer r.Close()
res, err := ioutil.ReadAll(r)
if err != nil {
return nil, err
}
return res, nil
}
Note, ioutil.ReadAll(r) returns io.EOF or io.ErrUnexpectedEOF if you do not close the Writer object after writing. I assumed defer on Close() would close the object properly, but it won't. Don't defer writer objects.