tee MultiWriter creates a writer that duplicates its writes to all the // provided writers, similar to the Unix tee(1) command.

https://zh.wikipedia.org/wiki/Tee

在计算机科学中，tee是一个常见的指令，它能够将某个指令的标准输出，导向、存入某个档案中。许多不同的命令行界面（Shell）都提供这个功能，如 Unix shell、Windows PowerShell。

tee的功能通常是用管道，让它不但能在萤幕输出，而且也能够将它储存在档案中。当一个资料在被另一个指令或程式改变之前的中间输出，也能够用tee来捕捉它。tee命令能够读取标准输入，之后将它的内容写入到标准输出，同时将它的副本写入特定的档案或变数中。

tee [ -a ] [ -i ] [檔案 ... ]

参数:

• 檔案 一个或多个档案，能够接收 tee-d 的输出。

Flags:

• -a 追加(append)到目标文件而不是覆盖
• -i 忽略中断。

[cpy@public ~]$ ll -as
总用量 32
 0 drwx------  10 cpy  cpy    206 12月 25 17:50 .
 0 drwxr-xr-x.  8 root root   111 12月 25 15:45 ..
12 -rw-------   1 cpy  cpy  12194 12月 23 19:58 .bash_history
 4 -rw-r--r--   1 cpy  cpy     18 8月   3 2016 .bash_logout
 4 -rw-r--r--   1 cpy  cpy    193 8月   3 2016 .bash_profile
 4 -rw-r--r--   1 cpy  cpy    231 8月   3 2016 .bashrc
 0 drwxrwxr-x   4 cpy  cpy     34 12月  9 19:12 .cache
 0 drwxrwxr-x   3 cpy  cpy     18 11月 25 11:53 .config
 4 -rw-rw-r--   1 cpy  cpy     35 12月 25 17:50 file
 0 drwxrwxr-x   7 cpy  cpy    120 12月 23 16:59 game_manager
 0 drwxrwxr-x   4 cpy  cpy     28 12月  9 19:12 go
 4 drwxrwxr-x  10 cpy  cpy   4096 11月 26 12:25 perfCCpp
 0 drwxrw----   3 cpy  cpy     19 12月  9 19:12 .pki
 0 drwxrwxr-x   5 cpy  cpy    176 12月 14 11:53 soft
 0 drwx------   2 cpy  cpy     25 11月 25 12:21 .ssh
[cpy@public ~]$ ll -as | tee file | cat
总用量 28
 0 drwx------  10 cpy  cpy    206 12月 25 17:50 .
 0 drwxr-xr-x.  8 root root   111 12月 25 15:45 ..
12 -rw-------   1 cpy  cpy  12194 12月 23 19:58 .bash_history
 4 -rw-r--r--   1 cpy  cpy     18 8月   3 2016 .bash_logout
 4 -rw-r--r--   1 cpy  cpy    193 8月   3 2016 .bash_profile
 4 -rw-r--r--   1 cpy  cpy    231 8月   3 2016 .bashrc
 0 drwxrwxr-x   4 cpy  cpy     34 12月  9 19:12 .cache
 0 drwxrwxr-x   3 cpy  cpy     18 11月 25 11:53 .config
 0 -rw-rw-r--   1 cpy  cpy      0 12月 25 17:51 file
 0 drwxrwxr-x   7 cpy  cpy    120 12月 23 16:59 game_manager
 0 drwxrwxr-x   4 cpy  cpy     28 12月  9 19:12 go
 4 drwxrwxr-x  10 cpy  cpy   4096 11月 26 12:25 perfCCpp
 0 drwxrw----   3 cpy  cpy     19 12月  9 19:12 .pki
 0 drwxrwxr-x   5 cpy  cpy    176 12月 14 11:53 soft
 0 drwx------   2 cpy  cpy     25 11月 25 12:21 .ssh
[cpy@public ~]$

　　

In computing, tee is a command in command-line interpreters (shells) using standard streams which reads standard input and writes it to both standard output and one or more files, effectively duplicating its input.^[1] It is primarily used in conjunction with pipes and filters. The command is named after the T-splitter used in plumbing.^[2]

 

 

Example usage of tee: The output of ls -l is redirected to tee which copies them to the file file.txt and to the pager less. The name tee comes from this scheme - it looks like the capital letter T

The tee command is normally used to split the output of a program so that it can be both displayed and saved in a file. The command can be used to capture intermediate output before the data is altered by another command or program. The tee command reads standard input, then writes its content to standard output. It simultaneously copies the result into the specified file(s) or variables. The syntax differs depending on the command's implementation.

io/multi.go

// MultiWriter creates a writer that duplicates its writes to all the
// provided writers, similar to the Unix tee(1) command.
//
// Each write is written to each listed writer, one at a time.
// If a listed writer returns an error, that overall write operation
// stops and returns the error; it does not continue down the list.
func MultiWriter(writers ...Writer) Writer {
   allWriters := make([]Writer, 0, len(writers))
   for _, w := range writers {
      if mw, ok := w.(*multiWriter); ok {
         allWriters = append(allWriters, mw.writers...)
      } else {
         allWriters = append(allWriters, w)
      }
   }
   return &multiWriter{allWriters}
}