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How to use Write method of log Package
Best Syzkaller code snippet using log.Write
handler.go
Source:handler.go 
...21 Order_Name string `json:"ordername"`22 Quantity string `json:"quantity"`23 UserID string `json:"id"`24}25func (h *Handler) CreateUser(w http.ResponseWriter, r *http.Request) {26 user := User{}27 dbConn, err := db.CreatConnection()28 if err != nil {29 h.Log.Error(err.Error())30 w.Write([]byte(err.Error()))31 w.WriteHeader(http.StatusInternalServerError)32 }33 defer dbConn.Close()34 if err := json.NewDecoder(r.Body).Decode(&user); err != nil {35 h.Log.Error(err.Error())36 w.Write([]byte("Cannot Decode request"))37 w.WriteHeader(http.StatusBadRequest)38 }39 insForm, err := dbConn.Prepare("INSERT INTO User(id, name, email, number) VALUES(?,?,?,?)")40 if err != nil {41 h.Log.Error(err.Error())42 w.Write([]byte("Cannot insert data"))43 w.WriteHeader(http.StatusInternalServerError)44 }45 _, err = insForm.Exec(user.Id, user.Name, user.Email, user.Phone_Number)46 if err != nil {47 h.Log.Error(err.Error())48 w.Write([]byte("Cannot insert data"))49 w.WriteHeader(http.StatusInternalServerError)50 }51}52func (h *Handler) FetchUser(w http.ResponseWriter, r *http.Request) {53 dbConn, err := db.CreatConnection()54 if err != nil {55 h.Log.Error(err.Error())56 w.Write([]byte(err.Error()))57 w.WriteHeader(http.StatusInternalServerError)58 }59 defer dbConn.Close()60 value := strings.Split(r.URL.Path, "/")[3]61 result, err := dbConn.Query("SELECT * FROM User WHERE id=?", value)62 if err != nil {63 h.Log.Error(err.Error())64 w.Write([]byte(err.Error()))65 w.WriteHeader(http.StatusInternalServerError)66 }67 user := User{}68 for result.Next() {69 var id, name, email, number string70 err = result.Scan(&id, &name, &email, &number)71 if err != nil {72 h.Log.Error(err.Error())73 w.Write([]byte("Cannot read user data"))74 w.WriteHeader(http.StatusInternalServerError)75 }76 user.Id = id77 user.Name = name78 user.Email = email79 user.Phone_Number = number80 }81 jData, err := json.Marshal(user)82 if err != nil {83 h.Log.Error(err.Error())84 w.Write([]byte("Cannot unmarshal data fetched for user"))85 w.WriteHeader(http.StatusInternalServerError)86 }87 w.Header().Set("Content-Type", "application/json")88 w.Write(jData)89}90func (h *Handler) UpdateUser(w http.ResponseWriter, r *http.Request) {91 user := User{}92 if err := json.NewDecoder(r.Body).Decode(&user); err != nil {93 h.Log.Error(err.Error())94 w.Write([]byte("Cannot Decode request"))95 w.WriteHeader(http.StatusBadRequest)96 }97 var queryString = "UPDATE User SET "98 if user.Name != "" {99 queryString += "name=?"100 }101 if user.Email != "" {102 if user.Name != "" {103 queryString += ", "104 }105 queryString += "email=?"106 }107 if user.Phone_Number != "" {108 if user.Name != "" || user.Email != "" {109 queryString += ", "110 }111 queryString += "number=?"112 }113 queryString += " WHERE id=?"114 dbConn, err := db.CreatConnection()115 if err != nil {116 h.Log.Error(err.Error())117 w.Write([]byte(err.Error()))118 w.WriteHeader(http.StatusInternalServerError)119 }120 defer dbConn.Close()121 value := strings.Split(r.URL.Path, "/")[3]122 insForm, err := dbConn.Prepare(queryString)123 if err != nil {124 h.Log.Error(err.Error())125 w.Write([]byte("Cannot update user data"))126 w.WriteHeader(http.StatusInternalServerError)127 }128 if user.Name != "" && user.Email != "" && user.Phone_Number != "" {129 _, err = insForm.Exec(user.Name, user.Email, user.Phone_Number, value)130 } else if user.Name != "" && user.Email != "" {131 _, err = insForm.Exec(user.Name, user.Email, value)132 } else if user.Name != "" && user.Phone_Number != "" {133 _, err = insForm.Exec(user.Name, user.Phone_Number, value)134 } else if user.Email != "" && user.Phone_Number != "" {135 _, err = insForm.Exec(user.Email, user.Phone_Number, value)136 } else if user.Name != "" {137 _, err = insForm.Exec(user.Name, value)138 } else if user.Email != "" {139 _, err = insForm.Exec(user.Email, value)140 } else {141 _, err = insForm.Exec(user.Phone_Number, value)142 }143 if err != nil {144 h.Log.Error(err.Error())145 w.Write([]byte(err.Error()))146 w.WriteHeader(http.StatusInternalServerError)147 }148 w.WriteHeader(http.StatusOK)149}150func (h *Handler) FetchAllUsers(w http.ResponseWriter, r *http.Request) {151 user := User{}152 dbConn, err := db.CreatConnection()153 if err != nil {154 h.Log.Error(err.Error())155 w.Write([]byte(err.Error()))156 w.WriteHeader(http.StatusInternalServerError)157 }158 defer dbConn.Close()159 result, err := dbConn.Query("SELECT * FROM User ")160 if err != nil {161 h.Log.Error(err.Error())162 w.Write([]byte(err.Error()))163 w.WriteHeader(http.StatusInternalServerError)164 }165 for result.Next() {166 var id, name, email, number string167 err = result.Scan(&id, &name, &email, &number)168 if err != nil {169 h.Log.Error(err.Error())170 log.Fatal(err.Error())171 w.Write([]byte(err.Error()))172 w.WriteHeader(http.StatusInternalServerError)173 }174 user.Id = id175 user.Name = name176 user.Email = email177 user.Phone_Number = number178 jData, err := json.Marshal(user)179 if err != nil {180 h.Log.Error(err.Error())181 w.Write([]byte(err.Error()))182 w.WriteHeader(http.StatusInternalServerError)183 }184 w.Write(jData)185 }186}187func (h *Handler) CreateOrder(w http.ResponseWriter, r *http.Request) {188 order := Order{}189 dbConn, err := db.CreatConnection()190 if err != nil {191 h.Log.Error(err.Error())192 w.Write([]byte(err.Error()))193 w.WriteHeader(http.StatusInternalServerError)194 }195 defer dbConn.Close()196 if err := json.NewDecoder(r.Body).Decode(&order); err != nil {197 h.Log.Error(err.Error())198 w.Write([]byte("Cannot Decode request"))199 w.WriteHeader(http.StatusBadRequest)200 }201 insForm, err := dbConn.Prepare("INSERT INTO Order_inv(orderid, ordername, quantity, id) VALUES(?,?,?,?)")202 if err != nil {203 h.Log.Error(err.Error())204 w.Write([]byte(err.Error()))205 w.WriteHeader(http.StatusInternalServerError)206 }207 _, err = insForm.Exec(order.Order_Id, order.Order_Name, order.Quantity, order.UserID)208 if err != nil {209 h.Log.Error(err.Error())210 w.Write([]byte(err.Error()))211 w.WriteHeader(http.StatusInternalServerError)212 }213}214func (h *Handler) CancelOrder(w http.ResponseWriter, r *http.Request) {215 value := strings.Split(r.URL.Path, "/")[3]216 dbConn, err := db.CreatConnection()217 if err != nil {218 h.Log.Error(err.Error())219 w.Write([]byte(err.Error()))220 w.WriteHeader(http.StatusInternalServerError)221 }222 _, err = dbConn.Query("Delete FROM Order_inv WHERE orderid=?", value)223 if err != nil {224 h.Log.Error(err.Error())225 w.Write([]byte(err.Error()))226 w.WriteHeader(http.StatusInternalServerError)227 }228}229func (h *Handler) FetchAllOrders(w http.ResponseWriter, r *http.Request) {230 value := strings.Split(r.URL.Path, "/")[3]231 dbConn, err := db.CreatConnection()232 if err != nil {233 h.Log.Error(err.Error())234 w.Write([]byte(err.Error()))235 w.WriteHeader(http.StatusInternalServerError)236 }237 defer dbConn.Close()238 result, err := dbConn.Query("SELECT * FROM Order_inv WHERE id=?", value)239 if err != nil {240 h.Log.Error(err.Error())241 w.Write([]byte(err.Error()))242 w.WriteHeader(http.StatusInternalServerError)243 }244 for result.Next() {245 order := Order{}246 var orderid, ordername, quantity, id string247 err = result.Scan(&orderid, &ordername, &quantity, &id)248 if err != nil {249 panic(err.Error())250 }251 order.Order_Id = orderid252 order.Order_Name = ordername253 order.Quantity = quantity254 order.UserID = id255 jData, err := json.Marshal(order)256 if err != nil {257 h.Log.Error(err.Error())258 w.Write([]byte(err.Error()))259 w.WriteHeader(http.StatusInternalServerError)260 }261 w.Write(jData)262 }263}...
syslog.go
Source:syslog.go
...61 LOG_LOCAL562 LOG_LOCAL663 LOG_LOCAL764)65// A Writer is a connection to a syslog server.66type Writer struct {67 priority Priority68 tag string69 hostname string70 network string71 raddr string72 mu sync.Mutex // guards conn73 conn serverConn74}75// This interface and the separate syslog_unix.go file exist for76// Solaris support as implemented by gccgo. On Solaris you can not77// simply open a TCP connection to the syslog daemon. The gccgo78// sources have a syslog_solaris.go file that implements unixSyslog to79// return a type that satisfies this interface and simply calls the C80// library syslog function.81type serverConn interface {82 writeString(p Priority, hostname, tag, s, nl string) error83 close() error84}85type netConn struct {86 local bool87 conn net.Conn88}89// New establishes a new connection to the system log daemon. Each90// write to the returned writer sends a log message with the given91// priority and prefix.92func New(priority Priority, tag string) (w *Writer, err error) {93 return Dial("", "", priority, tag)94}95// Dial establishes a connection to a log daemon by connecting to96// address raddr on the specified network. Each write to the returned97// writer sends a log message with the given facility, severity and98// tag.99// If network is empty, Dial will connect to the local syslog server.100func Dial(network, raddr string, priority Priority, tag string) (*Writer, error) {101 if priority < 0 || priority > LOG_LOCAL7|LOG_DEBUG {102 return nil, errors.New("log/syslog: invalid priority")103 }104 if tag == "" {105 tag = os.Args[0]106 }107 hostname, _ := os.Hostname()108 w := &Writer{109 priority: priority,110 tag: tag,111 hostname: hostname,112 network: network,113 raddr: raddr,114 }115 w.mu.Lock()116 defer w.mu.Unlock()117 err := w.connect()118 if err != nil {119 return nil, err120 }121 return w, err122}123// connect makes a connection to the syslog server.124// It must be called with w.mu held.125func (w *Writer) connect() (err error) {126 if w.conn != nil {127 // ignore err from close, it makes sense to continue anyway128 w.conn.close()129 w.conn = nil130 }131 if w.network == "" {132 w.conn, err = unixSyslog()133 if w.hostname == "" {134 w.hostname = "localhost"135 }136 } else {137 var c net.Conn138 c, err = net.Dial(w.network, w.raddr)139 if err == nil {140 w.conn = &netConn{conn: c}141 if w.hostname == "" {142 w.hostname = c.LocalAddr().String()143 }144 }145 }146 return147}148// Write sends a log message to the syslog daemon.149func (w *Writer) Write(b []byte) (int, error) {150 return w.writeAndRetry(w.priority, string(b))151}152// Close closes a connection to the syslog daemon.153func (w *Writer) Close() error {154 w.mu.Lock()155 defer w.mu.Unlock()156 if w.conn != nil {157 err := w.conn.close()158 w.conn = nil159 return err160 }161 return nil162}163// Emerg logs a message with severity LOG_EMERG, ignoring the severity164// passed to New.165func (w *Writer) Emerg(m string) (err error) {166 _, err = w.writeAndRetry(LOG_EMERG, m)167 return err168}169// Alert logs a message with severity LOG_ALERT, ignoring the severity170// passed to New.171func (w *Writer) Alert(m string) (err error) {172 _, err = w.writeAndRetry(LOG_ALERT, m)173 return err174}175// Crit logs a message with severity LOG_CRIT, ignoring the severity176// passed to New.177func (w *Writer) Crit(m string) (err error) {178 _, err = w.writeAndRetry(LOG_CRIT, m)179 return err180}181// Err logs a message with severity LOG_ERR, ignoring the severity182// passed to New.183func (w *Writer) Err(m string) (err error) {184 _, err = w.writeAndRetry(LOG_ERR, m)185 return err186}187// Warning logs a message with severity LOG_WARNING, ignoring the188// severity passed to New.189func (w *Writer) Warning(m string) (err error) {190 _, err = w.writeAndRetry(LOG_WARNING, m)191 return err192}193// Notice logs a message with severity LOG_NOTICE, ignoring the194// severity passed to New.195func (w *Writer) Notice(m string) (err error) {196 _, err = w.writeAndRetry(LOG_NOTICE, m)197 return err198}199// Info logs a message with severity LOG_INFO, ignoring the severity200// passed to New.201func (w *Writer) Info(m string) (err error) {202 _, err = w.writeAndRetry(LOG_INFO, m)203 return err204}205// Debug logs a message with severity LOG_DEBUG, ignoring the severity206// passed to New.207func (w *Writer) Debug(m string) (err error) {208 _, err = w.writeAndRetry(LOG_DEBUG, m)209 return err210}211func (w *Writer) writeAndRetry(p Priority, s string) (int, error) {212 pr := (w.priority & facilityMask) | (p & severityMask)213 w.mu.Lock()214 defer w.mu.Unlock()215 if w.conn != nil {216 if n, err := w.write(pr, s); err == nil {217 return n, err218 }219 }220 if err := w.connect(); err != nil {221 return 0, err222 }223 return w.write(pr, s)224}225// write generates and writes a syslog formatted string. The226// format is as follows: <PRI>TIMESTAMP HOSTNAME TAG[PID]: MSG227func (w *Writer) write(p Priority, msg string) (int, error) {228 // ensure it ends in a \n229 nl := ""230 if !strings.HasSuffix(msg, "\n") {231 nl = "\n"232 }233 err := w.conn.writeString(p, w.hostname, w.tag, msg, nl)234 if err != nil {235 return 0, err236 }237 // Note: return the length of the input, not the number of238 // bytes printed by Fprintf, because this must behave like239 // an io.Writer.240 return len(msg), nil241}242func (n *netConn) writeString(p Priority, hostname, tag, msg, nl string) error {243 if n.local {244 // Compared to the network form below, the changes are:245 // 1. Use time.Stamp instead of time.RFC3339.246 // 2. Drop the hostname field from the Fprintf.247 timestamp := time.Now().Format(time.Stamp)248 _, err := fmt.Fprintf(n.conn, "<%d>%s %s[%d]: %s%s",249 p, timestamp,250 tag, os.Getpid(), msg, nl)251 return err252 }253 timestamp := time.Now().Format(time.RFC3339)...
write_err_android.go
Source:write_err_android.go
...35 logger = legacy36 initLegacy()37 }38 }39 // Write to stderr for command-line programs.40 write(2, unsafe.Pointer(&b[0]), int32(len(b)))41 // Log format: "<header>\x00<message m bytes>\x00"42 //43 // <header>44 // In legacy mode: "<priority 1 byte><tag n bytes>".45 // In logd mode: "<android_log_header_t 11 bytes><priority 1 byte><tag n bytes>"46 //47 // The entire log needs to be delivered in a single syscall (the NDK48 // does this with writev). Each log is its own line, so we need to49 // buffer writes until we see a newline.50 var hlen int51 switch logger {52 case logd:53 hlen = writeLogdHeader()54 case legacy:55 hlen = len(writeHeader)56 }57 dst := writeBuf[hlen:]58 for _, v := range b {59 if v == 0 { // android logging won't print a zero byte60 v = '0'61 }62 dst[writePos] = v63 writePos++64 if v == '\n' || writePos == len(dst)-1 {65 dst[writePos] = 066 write(writeFD, unsafe.Pointer(&writeBuf[0]), int32(hlen+writePos))67 for i := range dst {68 dst[i] = 069 }70 writePos = 071 }72 }73}74func initLegacy() {75 // In legacy mode, logs are written to /dev/log/main76 writeFD = uintptr(open(&writePath[0], 0x1 /* O_WRONLY */, 0))77 if writeFD == 0 {78 // It is hard to do anything here. Write to stderr just79 // in case user has root on device and has run80 // adb shell setprop log.redirect-stdio true81 msg := []byte("runtime: cannot open /dev/log/main\x00")82 write(2, unsafe.Pointer(&msg[0]), int32(len(msg)))83 exit(2)84 }85 // Prepopulate the invariant header part.86 copy(writeBuf[:len(writeHeader)], writeHeader)87}88// used in initLogdWrite but defined here to avoid heap allocation.89var logdAddr sockaddr_un90func initLogd() {91 // In logd mode, logs are sent to the logd via a unix domain socket.92 logdAddr.family = _AF_UNIX93 copy(logdAddr.path[:], writeLogd)94 // We are not using non-blocking I/O because writes taking this path95 // are most likely triggered by panic, we cannot think of the advantage of96 // non-blocking I/O for panic but see disadvantage (dropping panic message),97 // and blocking I/O simplifies the code a lot.98 fd := socket(_AF_UNIX, _SOCK_DGRAM|_O_CLOEXEC, 0)99 if fd < 0 {100 msg := []byte("runtime: cannot create a socket for logging\x00")101 write(2, unsafe.Pointer(&msg[0]), int32(len(msg)))102 exit(2)...
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