c - C 中的文件操作给出奇怪的输出

Question

我正在运行一段 C 代码，该代码从 10 Dynamixel 获取信息。伺服电机(ID、位置、角度、负载扭矩)并将其打印到屏幕上，并将其写入日志文件(watchdog_log.txt)。

#include <stdio.h>
#include <stdlib.h>
#include <termio.h>
#include <unistd.h>
#include <string.h>
#include <dynamixel.h>
#include <math.h>
#include <dynamixelAX.h>
#include "utils_v2.h"
#include "low_level_v2AX.h"
#include "low_level_v2.h"


// Control table address
#define P_GOAL_POSITION_L       30
#define P_GOAL_POSITION_H       31
#define P_PRESENT_POSITION_L    36
#define P_PRESENT_POSITION_H    37
#define P_MOVING                46


// Defulat setting
#define DEFAULT_BAUDNUM         34 // 1Mbps
#define DEFAULT_BAUDNUM_AX  1
#define DEFAULT_ID              1


int main()
{
  FILE *fp;

  /* Get actuator ID from command line argument */
  int baudnum = 34;
  int baudnum_AX = 1;
  int deviceIndex = 0;
  int deviceIndex_AX = 1;
  int current;
  float load, angle;

  int i=0;
  int MOTOR_CHAIN[13]={-1,1,1,0,0,0,-1,1,1,0,0,0,-1};
  int MOTOR_CHAIN_AX[18]={2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2}; 
  int MOTOR_HOME[13]={404,444,3216,2037,2289,512,860,661,879,3474,1747,512};  //0, 6 and 12 are dummy
  int MOTOR_HOME_AX[18]={512,512,512,512,512,512,512,512,512,512,512,512,512,512,512,512,512,512,};

  char report[1000];
  char buffer[50];


  strcpy(report,"***********\n");

  /* Initialise Open USB2Dynamixel */
  if( dxl_initialize(deviceIndex, baudnum) == 0 )
    {
      printf( "Failed to open USB2Dynamixel!-chain'0'\n" );
      printf( "Press Enter key to terminate...\n" );

    }
  else
    printf( "Successfully opened USB2Dynamixel 0!\n" );

 if( dxl_initializeAX(deviceIndex_AX, baudnum_AX) == 0 )
    {
      printf( "Failed to open USB2Dynamixel!-chain'1'\n" );
      printf( "Press Enter key to terminate...\n" );
    }
  else
    printf( "Successfully opened USB2Dynamixel 1!\n" );


  /*  Ping all devices */
  printf("Pinging devices...");

  for( i=0; i<=12; i++)
  {
    dxl_ping(i);

   if (dxl_get_result() == COMM_RXSUCCESS)
   { 
    current = (fabs(dxl_read_word(i, 0x34)-512)*10);
    load = dxl_read_word(i, 0x28);
    if (load>=1024)
    load=(load-1024)*0.1;
    else load=load*0.1;

    int theta = dxl_read_word(i, 36);
    angle = counttoangle(MOTOR_CHAIN[i], MOTOR_HOME[i], theta);
    printf("ID: %d success,      Load:  %3.1f,       Count =  %d,     Angle =   %3.2f\n", i, load, theta, angle) ;
    sprintf(buffer,"ID: %d success,      Load:  %3.1f,       Count =  %d,     Angle =   %3.2f\n",i, load, theta, angle);
    strcat(report,buffer);

   }
  else printf("ID: %d failure\n",i);
 }


//File operations
strcat(report,"***********\n\n\n");

fp = fopen("watchdog_log.txt","w"); /* append file (add text to a file or create a file if it does not exist.*/ 
fprintf(fp,"%s",report); /*writes to file*/
fclose(fp); /*done!*/** 

 /* Close device */
  dxl_terminateAX();
  return 0;
  }

我在 Ubuntu 上使用“watch”命令每秒运行一次代码，以持续监控屏幕上代码的输出。

watch -n 1 ./watchdog

未进行文件操作时，终端输出正常。但是当文件写入完成后，终端会给出奇怪的输出:

正常输出

奇怪的输出

任何有关上述问题的帮助将不胜感激。

Answer 1

乍一看问题出在你的变量中:字符报告[1000];字符缓冲区[50];

当你和他们一起工作时，他们会溢出。例如sprintf(buffer,"ID: %d 成功, 加载: %3.1f, 计数 = %d, 角度 = %3.2f\n",i, 加载, theta, 角度);字符串的最小大小大于 50 个字节!因此，您可以尝试增加字符串变量的大小或计算所需的大小并将它们分配在堆中......