ioutilWriteFile

ioutil.WriteFile is a function from the Go standard library's ioutil package used to write data to a file in a single call. The function has the signature: WriteFile(filename string, data []byte, perm fs.FileMode) error. It writes the contents of data to the named file, creating the file if it does not exist and truncating it if it already exists. The perm parameter specifies the file mode bits for newly created files and follows the same semantics as os.OpenFile, subject to the process umask.

Behavior and semantics: If the write succeeds, the function returns nil. If the write fails, the function closes the file and returns an error. It writes all bytes from data; if a partial write occurs, an error is returned. If the directory path does not exist, an error is returned. In practice, this function is equivalent to opening the file with O_WRONLY|O_CREATE|O_TRUNC, writing the data, and closing the file.

Deprecation and alternatives: As of Go 1.16, the ioutil package is deprecated. WriteFile is deprecated in favor of the os.WriteFile function, which provides the same behavior and signature context, but resides in the os package. New code is encouraged to use os.WriteFile instead of ioutil.WriteFile.

Examples: data := []byte("example content"); if err := ioutil.WriteFile("example.txt", data, 0644); err != nil { // handle error }. For new code, use os.WriteFile("example.txt", data, 0644) with the same error handling.

See also: os.WriteFile, os.OpenFile, and related file I/O in the Go standard library.