Golang CSV在Linux上写为空

Question

I have a problem of writing csv file on linux, with exactly the same code, it works on windows but nothing is written to the file on linux(Centos7):

package main

import (
    "os"
    "fmt"
    "encoding/csv"
)

var data = [][]string{
    {"1","2","3","4","5"},
    {"a","b","c","d","f"},
}


func main() {
    filename := "example.csv"
    fp,e := os.OpenFile(filename, os.O_CREATE|os.O_APPEND, os.ModePerm)
    if nil != e {
        fmt.Printf("Open file '%s' failed: %s
", filename, e)
        os.Exit(1)
    }
    defer fp.Close()
    w := csv.NewWriter(fp)
    defer w.Flush()
    for _,l := range data {
        if e := w.Write(l); nil != e {
            fmt.Printf("Write csv failed: %s
",e)
            os.Exit(1)
        }
    }
    fmt.Println("Done.")
}

Answer 1

Golang spec described OpenFile:

OpenFile is the generalized open call; most users will use Open or Create instead. It opens the named file with specified flag (O_RDONLY etc.) and perm (before umask), if applicable. If successful, methods on the returned File can be used for I/O. If there is an error, it will be of type *PathError.

You are missing the flag to write to the file created using OpenFile function that's the reason file is opened for writing or reading but nothing is written to the csv.

package main

import (
    "encoding/csv"
    "fmt"
    "os"
)

var data = [][]string{
    {"1", "2", "3", "4", "5"},
    {"a", "b", "c", "d", "f"},
}

func main() {
    filename := "example.csv"
    fp, e := os.OpenFile(filename, os.O_CREATE|os.O_APPEND|os.O_WRONLY, os.ModePerm)
    if nil != e {
        fmt.Printf("Open file '%s' failed: %s
", filename, e)
        os.Exit(1)
    }
    defer fp.Close()
    w := csv.NewWriter(fp)
    defer w.Flush()
    for _, l := range data {
        if e := w.Write(l); nil != e {
            fmt.Printf("Write csv failed: %s
", e)
            os.Exit(1)
        }
    }
    fmt.Println("Done.")
}

Playground Example

Flags are elaborated in source code for os/file.go:

// Flags to OpenFile wrapping those of the underlying system. Not all

// flags may be implemented on a given system.

const (
    // Exactly one of O_RDONLY, O_WRONLY, or O_RDWR must be specified.
    O_RDONLY int = syscall.O_RDONLY // open the file read-only.
    O_WRONLY int = syscall.O_WRONLY // open the file write-only.
    O_RDWR   int = syscall.O_RDWR   // open the file read-write.
    // The remaining values may be or'ed in to control behavior.
    O_APPEND int = syscall.O_APPEND // append data to the file when writing.
    O_CREATE int = syscall.O_CREAT  // create a new file if none exists.
    O_EXCL   int = syscall.O_EXCL   // used with O_CREATE, file must not exist.
    O_SYNC   int = syscall.O_SYNC   // open for synchronous I/O.
    O_TRUNC  int = syscall.O_TRUNC  // if possible, truncate file when opened.

)