Related actions for summary files

* * We in the file related operations, often do not understand in which case the use of those functions, each check Baidu lead to inefficient development, I here to enumerate some convenient later query: * * * * * * * * * * * * * * * * * * * * * from a file location, read, write n characters * * * Copy a file to another file, or copy the first n characters of a file to another file * * * * * Aggregation of multiple files into a single file * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * , last modified time, absolute path, rename operation, existence) * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * to write the contents of a file to another file, you can control write content ****1, read the entire file * * ' Gofunc test1 Open ("D:/a.txt") if err! = Nil {panic (err)}defer f.close ()//Read entire file 1. Use Stat to get the file length, then open up space, write the data into the variable, output to the terminal fi, err: = F.stat () if err! = Nil {panic (err)}b: = Make ([]byte, FI. Size ()) If _, err = F.read (b); Err! = Nil {panic (err)}os. Stdout.write (b)//Read entire file 2. Directly using Ioutil's ReadAll function B, err = Ioutil. ReadAll (f) if err! = Nil {panic (err)}os. Stdout.write (b)} ' **2, starting from a location in the file, reading and writing n characters operation * * ' Gofunc test2 () {f, err: = OS. OpenFile ("D:/a.txt", OS. O_RDWR, 0755) if err! = Nil {panic (err)}defer f.close ()//sets the current position of the action file to the 10th character if _, err: = F.seek ( -10, Io. Seekend); Err! = Nil {panic (ERR)}//reads 5 characters from the current position B: = make ([]byte, Ten) If _, Err: = F.readat (b, 5); Err! = Nil {panic (err)}os. StdoUt. Write (b)//writes 5 characters from the current position (equivalent to overwriting the last 5 characters of a file) F. Writeat (b, 5)} "**3, copy the file to another file, or copy the first n characters of the file to another file * * *" "Gofunc test3 () {f1, err: = OS. Open ("D:/a.txt") if err! = Nil {panic (err)}defer F1. Close () F2, err: = OS. OpenFile ("D:/b.txt", OS. O_create | Os. O_RDWR, 0755) if err! = Nil {panic (err)}defer F2. Close ()//Copy all characters of F1 to the front of F2, if the size of F2 is larger than F1, then the following characters remain//if you want to append in F2, use the OS. O_appendif _, Err: = Io. Copy (F2, F1); Err! = Nil {panic (err)}//copies the n characters of F1 to the front of the F2 if _, err: = Io. Copyn (F2, F1, 10); Err! = Nil {panic (err)}} ' **4, aggregating multiple files into one file for operation * * ' Gofunc test4 () {f1, err: = OS. Open ("D:/a.txt") if err! = Nil {panic (err)}defer F1. Close () F2, err: = OS. Open ("D:/b.txt") if err! = Nil {panic (err)}defer F2. Close ()//will be 2 file. Reade merged into a readerr: = Io. Multireader (f1, F2)//poll read data in reader buf: = make ([]byte] Data: = Make ([]byte, 0, +) for n, err: = R.read (BUF); Err! = Io. EOF; N, err = R.read (buf) {if err! = Nil {panic (err)}data = append (data, Buf[:n] ...)} Os. Stdout.write (data)} ' **5, writes multiple characters simultaneously to multiple files * * ' Gofunc test5 () {f, err: = Os. OpenFile ("D:/a.txt", OS. O_create | Os. O_rdwr | Os. O_append, 0755) if err! = Nil {panic (err)}defer f.close ()//combines file and standard output into a writer w: = io. Multiwriter (f, OS. Stdout)//write every write to W contained in all writers. Write ([]byte ("HelloWorld")) W.write ([]byte ("Nihaoshijie")} "**6, get information about the file (name, size, whether it is a folder, file permissions, creation, last access, last modified time, Absolute path, rename operation, existence) * * ' Gofunc Test6 () {f, err: = OS. OpenFile ("D:/a.txt", OS. O_create|os. O_RDWR, 0755) if err! = Nil {panic (err)}defer f.close () fi, err: = F.stat () if err! = Nil {panic (err)}//name, size, whether folder, details, file permissions, last modification time FMT. Printf ("Name:%s\n", fi. Name ()) fmt. Printf ("Size:%d\n", fi. Size ()) fmt. Printf ("Isdir:%t\n", fi. Isdir ()) fmt. Printf ("SYS:%v\n", fi. Sys ()) fmt. Printf ("mode:%o\n", fi.) Mode ()) fmt. Printf ("Modtime:%s\n", fi. Modtime ())//Get details of the file creation time, detailed information see stat_t structure (different Windows and Linux)//windows//createtiontimeuint32// Lastaccesstimeuint32if reflect. ValueOf (FI. Sys ()). Elem (). Fieldbyname ("Createtiontime"). IsValid () {ctim: = reflect. ValueOf (FI. Sys ()). Elem (). Fieldbyname ("Createtiontime"). Field (0).Uint () fmt. Printf ("Ctim:%d\n", Ctim)}//gets the absolute path to the file dir, err: = FilePath. Abs ("D:/a.txt") if err! = Nil {panic (err)}fmt. Printf ("dir:%s\n", dir)//Determine if the file does not exist if _, err: = OS. Stat ("D:/c.txt"); Err! = Nil {if OS. Isnotexist (Err) {FMT. PRINTLN ("File not Exist")} else {panic (err)}}//rename file or folder (to have permission/file closed) If err: = OS. Rename ("D:/b.txt", "d:/d.txt"); Err! = Nil {panic (err)}} ' **7, get all files for folder * * ' Gofunc test7 () {files, err: = Ioutil. ReadDir ("d:/") if err! = Nil {panic (err)}//gets information about all files and folders under the folder for _, F: = Range files {fmt. Printf ("Name:%s, size:%d, Isdir:%t\n", F.name (), F.size (), F.isdir ())}} ' **8, writes the contents of one file to another file, and can control the writing of the content * * ' Gofunc Test8 () {f1, err: = OS. Open ("D:/a.txt") if err! = Nil {panic (err)}defer F1. Close () F2, err: = OS. OpenFile ("D:/b.txt", OS. O_create | Os. O_rdwr | Os. O_append, 0755) if err! = Nil {panic (err)}defer F2. The Close ()//setting will read from F1 to F2 in r: = Io. Teereader (f1, F2)//Loop 5 reads F1 the front 100 characters, each read will be automatically written to F2 for I: = 0; I < 5; i++ {F1. Seek (0, Io. Seekstart) If _, Err: = R.read (Make ([]byte, 100)); ERR! = Nil {if Err = = Io. Eof{return}panic (Err)}time. Sleep (time. Second)}} "The case is from:" Go language standard library "https://books.studygolang.com/The-Golang-Standard-Library-by-Example/chapter01/ 01.1.html64 Times Click