Go Package os
External
Internal
Overview
Reading and Writing an Entire File in/from Memory
Read with ReadFile()
To read the content of an entire file into a byte slice:
bs, err := os.ReadFile("/Users/ovidiu/tmp/test.txt")
os.ReadFile() closes the file after use.
Write with WriteFile()
To write in-memory data into a file:
s := "This\nis multi-line\nfile\ncontent\n"
err := os.WriteFile("/Users/ovidiu/tmp/test2.txt", []byte(s), 0777)
os.WriteFile() closes the file after use.
Sequentially Reading and Writing Byte Arrays
Reading
Open the file with os.Open() and then use the File Read() method to read into a byte slice.
bs := make([]byte, 10)
f, err := os.Open("/Users/ovidiu/tmp/test.txt")
if err != nil {
// ...
return
}
defer f.Close()
for {
cnt, err := f.Read(bs)
if err != nil {
fmt.Println(err)
f.Close()
return
}
fmt.Println("read ", cnt, " bytes")
}
The file must be explicitly closed after use with Close().
Writing
os.Create()
Open the file with os.Create(). It will return a os.File that implements io.Reader, io.Writer and io.Closer interfaces.
Then use the File Write() method write the content of a byte slice, or WriteString() to write strings. The file must be explicitly closed after use with Close():
var err error
f, err := os.Create("/Users/ovidiu/tmp/test3.txt")
if err != nil {
// ...
}
_, err = f.WriteString("This is the first line\n")
if err != nil {
// ...
}
_, err = f.WriteString("This is the second line\n")
if err != nil {
// ...
}
err = f.Close()
if err != nil {
// ...
}
The file content will be:
This is the first line
This is the second line
What happens if open the file with os.Open() and then I write?
Close
TO DEPLETE
Functions
os.File
os.File Methods
FileInfo
FileInfo Methods
- Size()
os.Args
os.Args is a string slice that holds the command-line arguments, starting with the program name. For more details on how to use see: