github.com/cellofellow/gopkg@v0.0.0-20140722061823-eec0544a62ad/glog/glog_file.go (about) 1 // Go support for leveled logs, analogous to https://code.google.com/p/google-glog/ 2 // 3 // Copyright 2013 Google Inc. All Rights Reserved. 4 // 5 // Licensed under the Apache License, Version 2.0 (the "License"); 6 // you may not use this file except in compliance with the License. 7 // You may obtain a copy of the License at 8 // 9 // http://www.apache.org/licenses/LICENSE-2.0 10 // 11 // Unless required by applicable law or agreed to in writing, software 12 // distributed under the License is distributed on an "AS IS" BASIS, 13 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 // See the License for the specific language governing permissions and 15 // limitations under the License. 16 17 // File I/O for logs. 18 19 package glog 20 21 import ( 22 "errors" 23 "flag" 24 "fmt" 25 "os" 26 "os/user" 27 "path/filepath" 28 "strings" 29 "sync" 30 "time" 31 ) 32 33 // MaxSize is the maximum size of a log file in bytes. 34 var MaxSize uint64 = 1024 * 1024 * 1800 35 36 // logDirs lists the candidate directories for new log files. 37 var logDirs []string 38 39 // If non-empty, overrides the choice of directory in which to write logs. 40 // See createLogDirs for the full list of possible destinations. 41 var logDir = flag.String("log_dir", "", "If non-empty, write log files in this directory") 42 43 func createLogDirs() { 44 if *logDir != "" { 45 logDirs = append(logDirs, *logDir) 46 } 47 logDirs = append(logDirs, os.TempDir()) 48 } 49 50 var ( 51 pid = os.Getpid() 52 program = filepath.Base(os.Args[0]) 53 host = "unknownhost" 54 userName = "unknownuser" 55 ) 56 57 func init() { 58 h, err := os.Hostname() 59 if err == nil { 60 host = shortHostname(h) 61 } 62 63 current, err := user.Current() 64 if err == nil { 65 userName = current.Username 66 } 67 68 // Sanitize userName since it may contain filepath separators on Windows. 69 userName = strings.Replace(userName, `\`, "_", -1) 70 } 71 72 // shortHostname returns its argument, truncating at the first period. 73 // For instance, given "www.google.com" it returns "www". 74 func shortHostname(hostname string) string { 75 if i := strings.Index(hostname, "."); i >= 0 { 76 return hostname[:i] 77 } 78 return hostname 79 } 80 81 // logName returns a new log file name containing tag, with start time t, and 82 // the name for the symlink for tag. 83 func logName(tag string, t time.Time) (name, link string) { 84 name = fmt.Sprintf("%s.%s.%s.log.%s.%04d%02d%02d-%02d%02d%02d.%d", 85 program, 86 host, 87 userName, 88 tag, 89 t.Year(), 90 t.Month(), 91 t.Day(), 92 t.Hour(), 93 t.Minute(), 94 t.Second(), 95 pid) 96 return name, program + "." + tag 97 } 98 99 var onceLogDirs sync.Once 100 101 // create creates a new log file and returns the file and its filename, which 102 // contains tag ("INFO", "FATAL", etc.) and t. If the file is created 103 // successfully, create also attempts to update the symlink for that tag, ignoring 104 // errors. 105 func create(tag string, t time.Time) (f *os.File, filename string, err error) { 106 onceLogDirs.Do(createLogDirs) 107 if len(logDirs) == 0 { 108 return nil, "", errors.New("log: no log dirs") 109 } 110 name, link := logName(tag, t) 111 var lastErr error 112 for _, dir := range logDirs { 113 fname := filepath.Join(dir, name) 114 f, err := os.Create(fname) 115 if err == nil { 116 symlink := filepath.Join(dir, link) 117 os.Remove(symlink) // ignore err 118 os.Symlink(name, symlink) // ignore err 119 return f, fname, nil 120 } 121 lastErr = err 122 } 123 return nil, "", fmt.Errorf("log: cannot create log: %v", lastErr) 124 }