gopkg.in/hugelgupf/u-root.v9@v9.0.0-20180831063832-3f6f1057f09b/cmds/dmesg/dmesg.go (about)

     1  // Copyright 2012-2017 the u-root 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  // Read the system log.
     6  //
     7  // Synopsis:
     8  //     dmesg [-clear|-read-clear]
     9  //
    10  // Options:
    11  //     -clear: clear the log
    12  //     -read-clear: clear the log after printing
    13  package main
    14  
    15  import (
    16  	"flag"
    17  	"log"
    18  	"os"
    19  	"syscall"
    20  	"unsafe"
    21  )
    22  
    23  const (
    24  	_SYSLOG_ACTION_READ       = 2
    25  	_SYSLOG_ACTION_READ_ALL   = 3
    26  	_SYSLOG_ACTION_READ_CLEAR = 4
    27  	_SYSLOG_ACTION_CLEAR      = 5
    28  )
    29  
    30  var (
    31  	clear     bool
    32  	readClear bool
    33  )
    34  
    35  func init() {
    36  	flag.BoolVar(&clear, "clear", false, "Clear the log")
    37  	flag.BoolVar(&readClear, "read-clear", false, "Clear the log after printing")
    38  	flag.BoolVar(&readClear, "c", false, "Clear the log after printing")
    39  }
    40  
    41  func main() {
    42  	flag.Parse()
    43  	if clear && readClear {
    44  		log.Fatalf("cannot specify both -clear and -read-clear")
    45  	}
    46  
    47  	level := uintptr(_SYSLOG_ACTION_READ_ALL)
    48  	if clear {
    49  		level = _SYSLOG_ACTION_CLEAR
    50  	}
    51  	if readClear {
    52  		level = _SYSLOG_ACTION_READ_CLEAR
    53  	}
    54  
    55  	b := make([]byte, 256*1024)
    56  	amt, _, err := syscall.Syscall(syscall.SYS_SYSLOG, level, uintptr(unsafe.Pointer(&b[0])), uintptr(len(b)))
    57  	if err != 0 {
    58  		log.Fatalf("syslog failed: %v", err)
    59  	}
    60  
    61  	os.Stdout.Write(b[:amt])
    62  }