File operation in C giving bizzare output - c

Question

I'm running a piece of C code that takes information from 10 Dynamixel servo motors ( ID, position, angle , load-torque ) and prints them to the screen as well as writes it to a log file ( 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;
}
I am running the code every one second using 'watch' command on Ubuntu to constantly monitor the output of the code on the screen.
watch -n 1 ./watchdog
The output on the terminal is normal when file operations are not done. But when file writing is done, the terminal gives bizzare outputs:
Normal Output
Bizzare Output
Any help on the above problem will be appreciated.

Answer 1

At first glance probles is in your variables:
char report[1000];
char buffer[50];
they are overflowed whe you are working with them.
for example
sprintf(buffer,"ID: %d success, Load: %3.1f, Count = %d, Angle = %3.2f\n",i, load, theta, angle);
The minimum size of the string is greater than 50 bytes!
So you can try increase the size of your string vars or calc needed size and allocate them in heap ...