Garbage Value in File after write

Question

I am making a log function which stores in a file.

int log_func(char* msg)
{
    int log_fd=0;
    ssize_t write_ret=0;
    int close_logfile_ret=0;
    time_t result;
    char error_msg[MAX_LOG_MSG_LEN]={' '};
    log_fd = open("/home/pi/log_client.txt", O_CREAT|O_APPEND|O_WRONLY);
    if(log_fd==-1)
    {
        printf("log failed !!----file open");
        exit(1);
    }

    result = time(NULL);
    snprintf(error_msg,MAX_LOG_MSG_LEN,"DALI_Server:%s:%s",asctime(localtime(&result)),msg);
    write_ret = write(log_fd,error_msg,sizeof(error_msg));

    if(write_ret == -1)
    {
        printf("log failed !!---- write");
        exit(1);
    }

    close_logfile_ret = close(log_fd);
    if(close_logfile_ret == -1)
    {
        printf("log failed !!---- close");
        exit(1);
    }
    return 0;
}

Here the array error_msg has been initialized to 'space'. but when i write less characters to it I get following result.

input: log_func("DALI Server Started");log_func("File open/create..."); output in file:

DALI_Server:Thu Jan 16 16:53:56 2014
:DALI Server started ^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@DALI_Server:Thu Jan 16 16:54:06 2014
File open/create...^@^@^@^@^@^@^@^@^@..

Why are the garbage characters coming.

Answer 1

You write the whole error_msg array, even the contents after the string terminator. Instead you should use strlen to get the length of the string in the array, and only write that:

write_ret = write(log_fd, error_msg, strlen(error_msg));