How can I read a whole file into a string variable

Question

I have lots of small files  I don t want to read them line by line   Is there a function in Go that will read a whole file into a string variable

User · Accepted Answer

Use ioutil ReadFile   func ReadFile filename string     byte  error       ReadFile reads the file named by filename and returns the contents  A successful call   returns err    nil  not err    EOF  Because ReadFile reads the whole file  it does not treat   an EOF from Read as an error to be reported    You will get a   byte instead of a string  It can be converted if really necessary   s    string buf

User · Answer

This is how I did it   package main  import      fmt     os     bytes     log     func main        filerc  err    os Open  filename      if err    nil       log Fatal err          defer filerc Close       buf    new bytes Buffer     buf ReadFrom filerc     contents    buf String       fmt Print contents

User · Answer

If you just want the content as string  then the simple solution is to use the ReadFile function from the io ioutil package  This function returns a slice of bytes which you can easily convert to a string   package main  import        fmt       io ioutil     func main         b  err    ioutil ReadFile  file txt      just pass the file name     if err    nil           fmt Print err             fmt Println b     print the content as  bytes       str    string b     convert content to a  string       fmt Println str     print the content as a  string

User · Answer

I think the best thing to do  if you re really concerned about the efficiency of concatenating all of these files  is to copy them all into the same bytes buffer   buf    bytes NewBuffer nil  for    filename    range filenames     f       os Open filename     Error handling elided for brevity    io Copy buf  f               Error handling elided for brevity    f Close     s    string buf Bytes      This opens each file  copies its contents into buf  then closes the file   Depending on your situation you may not actually need to convert it  the last line is just to show that buf Bytes   has the data you re looking for

User · Answer

I m not with computer so I write a draft  You might be clear of what I say   func main        const dir     etc       filesInfo  e    ioutil ReadDir dir      var fileNames   make   string  0  10      for i v  range filesInfo          if  v IsDir                 fileNames   append fileNames  v Name                         var fileNumber   len fileNames      var contents   make   string  fileNumber  10      wg    sync WaitGroup       wg Add fileNumber       for i    range content           go func i int               defer wg Done               buf e    ioutil Readfile fmt Printf   s  s   dir  fileName i                defer file Close                 content i    string buf            i               wg Wait

[string] How can I read a whole file into a string variable

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