Golang file read/write

This is a creation in Article, where the information may have evolved or changed.

Read and write files, do not add file path, default write to Gopath path

Terminal Read and write:

Source

string string, a ... Interface int , err Error)

Explanation: 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"//terminal reading and writingType Studentstruct{Namestring Ageintscore Float32}func Main () {varstr ="stu01 89.92"    varStu student FMT. SSCANF (str,"%s%d%f", &stu. Name, &stu. Age, &Stu. Score) FMT. Println (Stu)}

Text I/O buffering:

Source

*newdefault size.

-

Package Mainimport ("Bufio"    "FMT"    "OS"Func Main () {reader:=Bufio. Newreader (OS. Stdin) str, err:= Reader. ReadString ('\ n')    ifErr! =Nil {fmt. Println ("Read String,err:", Err)return} fmt. Printf ("Read STR succ,ret:%s\n", str)}

Open file, read

Package Mainimport ("Bufio"    "FMT"    "OS")//Read FileFunc Main () {//Open a fileFile, err: = OS. Open ("D:/project/src/go_dev/day7/example4/123.log")    ifErr! =Nil {fmt. Println ("Read file err:", Err)return    }    //focus, file to closedefer 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)
If the file is not wrapped at the end, error str, err:= Reader. ReadString ('\ n')    ifErr! =Nil {fmt. Println ("Read string Failed,err:", Err)return} fmt. Printf ("Read STR success,result:%s\n", str)}

ReadString Source

    /*     func (*reader) Readstring¶func (b *reader) ReadString (Delim byte) (string, error) ReadString reads until the Firs T 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 Itse LF (often io. EOF).    ReadString returns ERR! = Nil if and only if the returned data does not end in Delim. For simple uses, a Scanner is more convenient.      */

-read the number of characters in a row

Package Mainimport ("FMT"    "OS")/*reads a line of strings from the terminal, counting the number of English, numbers, spaces, and other characters*/Import ("Bufio"    "io") Type CharCountstruct{ChcountintNumcountintSpacecountintOthercountint}func Main () {file, err:= OS. Open ("D:/project/src/go_dev/day7/example4/123.log")    ifErr! =Nil {fmt. Println ("Read file err:", Err)return} defer file. Close ()varCount CharCount Reader:=Bufio. Newreader (file) for{str, err:= Reader. ReadString ('\ n')        ifErr = =io. EOF { Break        }        ifErr! =Nil {fmt. Printf ("Read File Failed,err:%v", Err) Break} Runearr:=[]rune (str) for_, V: =Range Runearr {Switch {             CaseV >='a'&& v <='Z': Fallthrough CaseV >='A'&& v <='Z': Count. Chcount++ Casev = =' '|| v = ='\ t': Count. Spacecount++ CaseV >='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)}

Character Statistics

File Write

--

Package Mainimport ("Bufio"    "FMT"    "OS") Func main () {outputfile,outputerror:=os. OpenFile ("Output.dat", OS. O_wronly|os. O_create,0666)    ifoutputerror!=nil{FMT. Printf ("An error occurred with file Crea ion\n")        return    }    //be sure to close before the function is finished, and rememberdefer outputfile.close () Outputwriter:=Bufio. Newwriter (outputFile) outputstring:="Hello world!\n"     fori:=0;i<Ten; i++{outputwriter.writestring (outputstring)} outputwriter.flush ()//Refresh Floor}

Copy files for Golang

Package Mainimport ("FMT"    "io"    "OS") Func main () {//os. Args is a slice of string that is used to store all command-line argumentsW, err: = CopyFile (OS. args[1], OS. args[2])    ifErr! =Nil {fmt. Println (Err. Error ())} FMT. Println (W)}func CopyFile (DstName, SrcNamestring) (written int64, err error) {src, err:=OS. Open (SrcName)ifErr! =Nil {return} defer src. Close () DST, err:= OS. OpenFile (DstName, OS. O_wronly|os. O_create,0644)    ifErr! =Nil {return} defer DST. Close ()//write the src content into DST    returnio. Copy (DST, SRC)}

Command-line arguments

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)    }}

The flag package is used to implement command-line arguments

For example, Ls-l under Linux

Package Mainimport ("Flag"    "FMT")//Flag Package supports command-line argumentsFunc Main () {varConfpathstring    varLogLevelintflag. 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)}