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2017-02-06
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File I/O

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Syntax

  • file, err := os.Open(name) // Opens a file in read-only mode. A non-nil error is returned if the file could not be opened.
  • file, err := os.Create(name) // Creates or opens a file if it already exists in write-only mode. The file is overwritten to if it already exists. A non-nil error is returned if the file could not be opened.
  • file, err := os.OpenFile(name, flags, perm) // Opens a file in the mode specified by the flags. A non-nil error is returned if the file could not be opened.
  • data, err := ioutil.ReadFile(name) // Reads the entire file and returns it. A non-nil error is returned if the entire file could not be read.
  • err := ioutil.WriteFile(name, data, perm) // Creates or overwrites a file with the provided data and UNIX permission bits. A non-nil error is returned if the file failed to be written to.
  • err := os.Remove(name) // Deletes a file. A non-nil error is returned if the file could not be deleted.
  • err := os.RemoveAll(name) // Deletes a file or whole directory hierarchy. A non-nil error is returned if the file or directory could not be deleted.
  • err := os.Rename(oldName, newName) // Renames or moves a file (can be across directories). A non-nil error is returned if the file could not be moved.

Parameters

ParameterDetails
nameA filename or path of type string. For example: "hello.txt".
errAn error. If not nil, it represents an error that occurred when the function was called.
fileA file handler of type *os.File returned by the os package file related functions. It implements an io.ReadWriter, meaning you can call Read(data) and Write(data) on it. Note that these functions may not be able to be called depending on the open flags of the file.
dataA slice of bytes ([]byte) representing the raw data of a file.
permThe UNIX permission bits used to open a file with of type os.FileMode. Several constants are available to help with the use of permission bits.
flagFile open flags that determine the methods that can be called on the file handler of type int. Several constants are available to help with the use of flags. They are: os.O_RDONLY, os.O_WRONLY, os.O_RDWR, os.O_APPEND, os.O_CREATE, os.O_EXCL, os.O_SYNC, and os.O_TRUNC.

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