fileutil.go

Documentation: go.etcd.io/etcd/client/pkg/v3/fileutil

     1  // Copyright 2015 The etcd Authors
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package fileutil
    16  
    17  import (
    18  	"fmt"
    19  	"io"
    20  	"io/ioutil"
    21  	"os"
    22  	"path/filepath"
    23  
    24  	"go.uber.org/zap"
    25  )
    26  
    27  const (
    28  	// PrivateFileMode grants owner to read/write a file.
    29  	PrivateFileMode = 0600
    30  )
    31  
    32  // IsDirWriteable checks if dir is writable by writing and removing a file
    33  // to dir. It returns nil if dir is writable.
    34  func IsDirWriteable(dir string) error {
    35  	f, err := filepath.Abs(filepath.Join(dir, ".touch"))
    36  	if err != nil {
    37  		return err
    38  	}
    39  	if err := ioutil.WriteFile(f, []byte(""), PrivateFileMode); err != nil {
    40  		return err
    41  	}
    42  	return os.Remove(f)
    43  }
    44  
    45  // TouchDirAll is similar to os.MkdirAll. It creates directories with 0700 permission if any directory
    46  // does not exists. TouchDirAll also ensures the given directory is writable.
    47  func TouchDirAll(lg *zap.Logger, dir string) error {
    48  	// If path is already a directory, MkdirAll does nothing and returns nil, so,
    49  	// first check if dir exist with an expected permission mode.
    50  	if Exist(dir) {
    51  		err := CheckDirPermission(dir, PrivateDirMode)
    52  		if err != nil {
    53  			lg.Warn("check file permission", zap.Error(err))
    54  		}
    55  	} else {
    56  		err := os.MkdirAll(dir, PrivateDirMode)
    57  		if err != nil {
    58  			// if mkdirAll("a/text") and "text" is not
    59  			// a directory, this will return syscall.ENOTDIR
    60  			return err
    61  		}
    62  	}
    63  
    64  	return IsDirWriteable(dir)
    65  }
    66  
    67  // CreateDirAll is similar to TouchDirAll but returns error
    68  // if the deepest directory was not empty.
    69  func CreateDirAll(lg *zap.Logger, dir string) error {
    70  	err := TouchDirAll(lg, dir)
    71  	if err == nil {
    72  		var ns []string
    73  		ns, err = ReadDir(dir)
    74  		if err != nil {
    75  			return err
    76  		}
    77  		if len(ns) != 0 {
    78  			err = fmt.Errorf("expected %q to be empty, got %q", dir, ns)
    79  		}
    80  	}
    81  	return err
    82  }
    83  
    84  // Exist returns true if a file or directory exists.
    85  func Exist(name string) bool {
    86  	_, err := os.Stat(name)
    87  	return err == nil
    88  }
    89  
    90  // DirEmpty returns true if a directory empty and can access.
    91  func DirEmpty(name string) bool {
    92  	ns, err := ReadDir(name)
    93  	return len(ns) == 0 && err == nil
    94  }
    95  
    96  // ZeroToEnd zeros a file starting from SEEK_CUR to its SEEK_END. May temporarily
    97  // shorten the length of the file.
    98  func ZeroToEnd(f *os.File) error {
    99  	// TODO: support FALLOC_FL_ZERO_RANGE
   100  	off, err := f.Seek(0, io.SeekCurrent)
   101  	if err != nil {
   102  		return err
   103  	}
   104  	lenf, lerr := f.Seek(0, io.SeekEnd)
   105  	if lerr != nil {
   106  		return lerr
   107  	}
   108  	if err = f.Truncate(off); err != nil {
   109  		return err
   110  	}
   111  	// make sure blocks remain allocated
   112  	if err = Preallocate(f, lenf, true); err != nil {
   113  		return err
   114  	}
   115  	_, err = f.Seek(off, io.SeekStart)
   116  	return err
   117  }
   118  
   119  // CheckDirPermission checks permission on an existing dir.
   120  // Returns error if dir is empty or exist with a different permission than specified.
   121  func CheckDirPermission(dir string, perm os.FileMode) error {
   122  	if !Exist(dir) {
   123  		return fmt.Errorf("directory %q empty, cannot check permission", dir)
   124  	}
   125  	//check the existing permission on the directory
   126  	dirInfo, err := os.Stat(dir)
   127  	if err != nil {
   128  		return err
   129  	}
   130  	dirMode := dirInfo.Mode().Perm()
   131  	if dirMode != perm {
   132  		err = fmt.Errorf("directory %q exist, but the permission is %q. The recommended permission is %q to prevent possible unprivileged access to the data", dir, dirInfo.Mode(), os.FileMode(PrivateDirMode))
   133  		return err
   134  	}
   135  	return nil
   136  }
   137  
   138  // RemoveMatchFile deletes file if matchFunc is true on an existing dir
   139  // Returns error if the dir does not exist or remove file fail
   140  func RemoveMatchFile(lg *zap.Logger, dir string, matchFunc func(fileName string) bool) error {
   141  	if lg == nil {
   142  		lg = zap.NewNop()
   143  	}
   144  	if !Exist(dir) {
   145  		return fmt.Errorf("directory %s does not exist", dir)
   146  	}
   147  	fileNames, err := ReadDir(dir)
   148  	if err != nil {
   149  		return err
   150  	}
   151  	var removeFailedFiles []string
   152  	for _, fileName := range fileNames {
   153  		if matchFunc(fileName) {
   154  			file := filepath.Join(dir, fileName)
   155  			if err = os.Remove(file); err != nil {
   156  				removeFailedFiles = append(removeFailedFiles, fileName)
   157  				lg.Error("remove file failed",
   158  					zap.String("file", file),
   159  					zap.Error(err))
   160  				continue
   161  			}
   162  		}
   163  	}
   164  	if len(removeFailedFiles) != 0 {
   165  		return fmt.Errorf("remove file(s) %v error", removeFailedFiles)
   166  	}
   167  	return nil
   168  }
   169
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