ioutil.go

Documentation: io/ioutil

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Package ioutil implements some I/O utility functions.
     6  //
     7  // As of Go 1.16, the same functionality is now provided
     8  // by package io or package os, and those implementations
     9  // should be preferred in new code.
    10  // See the specific function documentation for details.
    11  package ioutil
    12  
    13  import (
    14  	"io"
    15  	"io/fs"
    16  	"os"
    17  	"sort"
    18  )
    19  
    20  // ReadAll reads from r until an error or EOF and returns the data it read.
    21  // A successful call returns err == nil, not err == EOF. Because ReadAll is
    22  // defined to read from src until EOF, it does not treat an EOF from Read
    23  // as an error to be reported.
    24  //
    25  // As of Go 1.16, this function simply calls io.ReadAll.
    26  func ReadAll(r io.Reader) ([]byte, error) {
    27  	return io.ReadAll(r)
    28  }
    29  
    30  // ReadFile reads the file named by filename and returns the contents.
    31  // A successful call returns err == nil, not err == EOF. Because ReadFile
    32  // reads the whole file, it does not treat an EOF from Read as an error
    33  // to be reported.
    34  //
    35  // As of Go 1.16, this function simply calls os.ReadFile.
    36  func ReadFile(filename string) ([]byte, error) {
    37  	return os.ReadFile(filename)
    38  }
    39  
    40  // WriteFile writes data to a file named by filename.
    41  // If the file does not exist, WriteFile creates it with permissions perm
    42  // (before umask); otherwise WriteFile truncates it before writing, without changing permissions.
    43  //
    44  // As of Go 1.16, this function simply calls os.WriteFile.
    45  func WriteFile(filename string, data []byte, perm fs.FileMode) error {
    46  	return os.WriteFile(filename, data, perm)
    47  }
    48  
    49  // ReadDir reads the directory named by dirname and returns
    50  // a list of fs.FileInfo for the directory's contents,
    51  // sorted by filename. If an error occurs reading the directory,
    52  // ReadDir returns no directory entries along with the error.
    53  //
    54  // As of Go 1.16, os.ReadDir is a more efficient and correct choice:
    55  // it returns a list of fs.DirEntry instead of fs.FileInfo,
    56  // and it returns partial results in the case of an error
    57  // midway through reading a directory.
    58  func ReadDir(dirname string) ([]fs.FileInfo, error) {
    59  	f, err := os.Open(dirname)
    60  	if err != nil {
    61  		return nil, err
    62  	}
    63  	list, err := f.Readdir(-1)
    64  	f.Close()
    65  	if err != nil {
    66  		return nil, err
    67  	}
    68  	sort.Slice(list, func(i, j int) bool { return list[i].Name() < list[j].Name() })
    69  	return list, nil
    70  }
    71  
    72  // NopCloser returns a ReadCloser with a no-op Close method wrapping
    73  // the provided Reader r.
    74  //
    75  // As of Go 1.16, this function simply calls io.NopCloser.
    76  func NopCloser(r io.Reader) io.ReadCloser {
    77  	return io.NopCloser(r)
    78  }
    79  
    80  // Discard is an io.Writer on which all Write calls succeed
    81  // without doing anything.
    82  //
    83  // As of Go 1.16, this value is simply io.Discard.
    84  var Discard io.Writer = io.Discard
    85
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