Golang之檔案讀寫

這是一個建立於 的文章，其中的資訊可能已經有所發展或是發生改變。

讀寫檔案，不添加檔案路徑，預設寫入到GOPATH路徑下

終端讀寫:

源碼

func Sscanffunc Sscanf(str string, format string, a ...interface{}) (n int, err error)

解釋：Sscanf scans the argument string, storing successive space-separated values into successive arguments as determined by the format.
It returns the number of items successfully parsed. Newlines in the input must match newlines in the format.

package mainimport "fmt"//終端讀寫type student struct {    Name  string    Age   int    Score float32}func main() {    var str = "stu01 18 89.92"    var stu student    fmt.Sscanf(str, "%s %d %f", &stu.Name, &stu.Age, &stu.Score)    fmt.Println(stu)}

文本I/O緩衝：

源碼

func NewReaderfunc NewReader(rd io.Reader) *ReaderNewReader returns a new Reader whose buffer has the default size.

-

package mainimport (    "bufio"    "fmt"    "os")func main() {    reader := bufio.NewReader(os.Stdin)    str, err := reader.ReadString('\n')    if err != nil {        fmt.Println("read string,err:", err)        return    }    fmt.Printf("read str succ,ret:%s\n", str)}

開啟檔案，讀取

package mainimport (    "bufio"    "fmt"    "os")//讀取檔案func main() {    //開啟一個檔案    file, err := os.Open("D:/project/src/go_dev/day7/example4/123.log")    if err != nil {        fmt.Println("read file err:", err)        return    }    //重點，檔案要關閉    defer file.Close()    /*        func NewReaderSize        func NewReaderSize(rd io.Reader, size int) *Reader            NewReaderSize returns a new Reader whose buffer has at least the specified size.            If the argument io.Reader is already a Reader with large enough size, it returns the underlying Reader.    */    reader := bufio.NewReader(file)
　　//檔案若不是換行結尾，就算出錯    str, err := reader.ReadString('\n')    if err != nil {        fmt.Println("read string failed,err:", err)        return    }    fmt.Printf("read str success,result:%s\n", str)}

ReadString源碼

    /*    func (*Reader) ReadString ¶func (b *Reader) ReadString(delim byte) (string, error)ReadString reads until the first occurrence of delim in the input, returning a string containing the data up to and including the delimiter.    If ReadString encounters an error before finding a delimiter, it returns the data read before the error and the error itself (often io.EOF).    ReadString returns err != nil if and only if the returned data does not end in delim. For simple uses, a Scanner may be more convenient.     */

 -讀取一行的字元個數

package mainimport (    "fmt"    "os")/*從終端讀取一行字串，統計英文、數字、空格以及其他字元的數量*/import (    "bufio"    "io")type CharCount struct {    ChCount    int    NumCount   int    SpaceCount int    OtherCount int}func main() {    file, err := os.Open("D:/project/src/go_dev/day7/example4/123.log")    if err != nil {        fmt.Println("read file err:", err)        return    }    defer file.Close()    var count CharCount    reader := bufio.NewReader(file)    for {        str, err := reader.ReadString('\n')        if err == io.EOF {            break        }        if err != nil {            fmt.Printf("read file failed,err:%v", err)            break        }        runeArr := []rune(str)        for _, v := range runeArr {            switch {            case v >= 'a' && v <= 'z':                fallthrough            case v >= 'A' && v <= 'Z':                count.ChCount++            case v == ' ' || v == '\t':                count.SpaceCount++            case v >= '0' && v <= '9':                count.NumCount++            default:                count.OtherCount++            }        }    }    fmt.Printf("char count:%d\n", count.ChCount)    fmt.Printf("num count:%d\n", count.NumCount)    fmt.Printf("space count:%d\n", count.SpaceCount)    fmt.Printf("other count:%d\n", count.OtherCount)}

字元統計

 檔案寫入

--

package mainimport (    "bufio"    "fmt"    "os")func main(){    outputFile,outputError:=os.OpenFile("output.dat",os.O_WRONLY|os.O_CREATE,0666)    if outputError!=nil{        fmt.Printf("An error occurred with file crea ion\n")        return    }    //在函數執行結束前，一定要關閉，謹記    defer outputFile.Close()    outputWriter:=bufio.NewWriter(outputFile)    outputString:="hello world!\n"    for i:=0;i<10;i++{        outputWriter.WriteString(outputString)    }    outputWriter.Flush()//重新整理落地}

golang的複製檔案

package mainimport (    "fmt"    "io"    "os")func main() {    //os.Args是string的切片，用來儲存所有的命令列參數    w, err := CopyFile(os.Args[1], os.Args[2])    if err != nil {        fmt.Println(err.Error())    }    fmt.Println(w)}func CopyFile(dstName, srcName string) (written int64, err error) {    src, err := os.Open(srcName)    if err != nil {        return    }    defer src.Close()    dst, err := os.OpenFile(dstName, os.O_WRONLY|os.O_CREATE, 0644)    if err != nil {        return    }    defer dst.Close()    //把src內容寫進dst裡面    return io.Copy(dst, src)}

命令列參數

package mainimport (    "fmt"    "os")func main() {    fmt.Printf("len of args:%d\n", len(os.Args))    for i, v := range os.Args {        fmt.Printf("args[%d]=%s\n", i, v)    }}

flag包用於實現命令列參數

例如Linux下的 ls -l

package mainimport (    "flag"    "fmt")//flag包支援命令列參數func main() {    var confPath string    var logLevel int    flag.StringVar(&confPath, "c", "", "Please input conf path")    flag.IntVar(&logLevel, "d", 0, "PLEASE INPUT LOG LEVEL")    flag.Parse()    fmt.Println("path：", confPath)    fmt.Println("log leve：", logLevel)}