带有O_CREATE标志的os.OpenFile不会抛出这样的文件或目录

Question

I'm trying to open a log file with os package using os.OpenFile function, which should with proper flag create file if such file does not exists. But it returns non nil error: No such file or directory. BTW I'm using linux and go 1.6. Log file opening happens in init function. Heres my code:

package main

import (
    "encoding/json"
    "fmt"
    "log"
    "net/http"
    "os"

    "github.com/gorilla/mux"
    "github.com/gorilla/sessions"
)

// Structs holds server configuration data from config json.
type serverConfiguration struct {
    port                    string
    logFileName             string
    sessionStorePhrase      string
    resourceFilesPath       string
    resourceFilesPathPrefix string
}

// Server global variables.
var (
    serverConfig serverConfiguration
    logFile      *os.File
    router       *mux.Router
    sessionStore *sessions.CookieStore
)

func init() {
    // temporary variables.
    var (
        configFile                                   *os.File
        serverConfErr, configDecodingErr, logFileErr error
    )

    // Loads json config file.
    configFile, serverConfErr = os.Open("server-conf.json")
    defer configFile.Close()

    if serverConfErr != nil {
        log.Fatal("SERVER-CONFIG-ERROR: ", serverConfErr)
    }

    // Decodes json to serverConfig struct.
    decoder := json.NewDecoder(configFile)
    serverConfig = serverConfiguration{}
    configDecodingErr = decoder.Decode(&serverConfig)

    if configDecodingErr != nil {
        log.Fatal("CONFIGURATION-DECODING-ERROR: ", configDecodingErr)
    }

    // Opens log file in app root directory.
    logFile, logFileErr = os.OpenFile(serverConfig.logFileName, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0666)

    if logFileErr != nil {
        log.Fatal("LOG-FILE-ERROR: ", logFileErr)
    }

    // Creates session store.
    sessionStore = sessions.NewCookieStore([]byte(serverConfig.sessionStorePhrase))
}

// Home page handler.
func homePageHandler(writer http.ResponseWriter, request *http.Request) {
    fmt.Fprint(writer, "asdasdasdasd")
}

func main() {
    defer logFile.Close()
    router = mux.NewRouter().StrictSlash(false)
    resourceFileServer := http.FileServer(http.Dir(serverConfig.resourceFilesPath))
    router.PathPrefix(serverConfig.resourceFilesPathPrefix).Handler(http.StripPrefix(serverConfig.resourceFilesPathPrefix, resourceFileServer))

    router.HandleFunc("/", homePageHandler)

    server := &http.Server{
        Addr:    serverConfig.port,
        Handler: router,
    }

    log.Println("Server listening on port ", serverConfig.port)
    server.ListenAndServe()
}

Answer 1

The error is most likely that the path you want to create your file in doesn't exist. it will create the logfile, but not the parent directories if they don't exist. To create the necessary directory structure, you could use os.MkdirAll