Golang: Read File

By Xah Lee. Date: . Last updated: .

Read Whole File

package main

import "fmt"
import "io/ioutil"

func main() {

	// read whole file
	myText, myErr := ioutil.ReadFile("/Users/x/filepath")

	if myErr != nil {
		panic(myErr)
		// panic means abort
	}

	// print it. String converts it to string
	fmt.Print(string(myText))

}

Read First X Bytes

package main

import "fmt"
import "os"

// open file. read first 200 bytes. print it.

var filePath = "/Users/xah/web/xahlee_info/golang/golang_read_file.html"

func getHeadBytes(path string, n int) []byte {

	file, err := os.Open(path) // For read access.
	if err != nil {
		panic(err)
	}

	defer file.Close()

	headBytes := make([]byte, n)
	m, err := file.Read(headBytes)
	if err != nil {
		panic(err)
	}

	return headBytes[:m]
}

func main() {

	fmt.Printf("%q\n", getHeadBytes(filePath, 200))

}

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Golang

  1. Compile, Run
  2. Source Encoding
  3. Package, Import
  4. Comment
  5. Print
  6. String
  7. String Functions
  8. Print String
  9. String Backslash Escape
  10. Rune
  11. Variable
  12. Zero Value
  13. Constant
  14. If Then Else
  15. Switch/Case
  16. Loop
  17. Basic Types
  18. Array
  19. Slice
  20. Map
  21. Struct
  22. Function
  23. Closure
  24. Pointer
  25. String, Byte Slice, Rune Slice
  26. regexp
  27. Read File
  28. Write to File
  29. Walk Dir
  30. Check File Exist
  31. System Call
  32. Get Script Path
  33. Defer
  34. Random Number

Examples

  1. Match Any Regexp
  2. Find Replace
  3. Validate Links
  4. Generate Sitemap

Reference

  1. Go Spec