C program reading and writing to binary files

Hello this is the first time I am working with binary file in C. So what I am trying to do is I a trying to first write the data to the file and then I am trying to read the same data from the file. But somehow I am not reading the data correctly (that's what I think) because I think so I am writing the data correctly. And I doing all of this in unix. So basically I am trying to write and read data from the binary file in unix and I am not able to read teh data properly. Any help would be appreciated. Thanks in advance. I am attaching the code and the output below so it is understandable.

#include <stdio.h>  #include <sys/types.h>  #include <fcntl.h>  #include <unistd.h>  #include <string.h>  #include <sys/stat.h>  #include <stdlib.h>  int main(int argc, char *argv[]){      char data[100];      //struct data my_data;      if(argc<2){               printf("Usage: gift <textstring>\n");       return -1;              }              int n = 0;              int num = 0;      //FILE *f;      //f = fopen("gifts.dat","r");      char data[100];      //struct data my_data;      if(argc<2){               printf("Usage: gift <textstring>\n");       return -1;              }              int n = 0;              int num = 0;      //FILE *f;      //f = fopen("gifts.dat","r");      int fd = open("gifts.dat", O_CREAT | O_WRONLY | O_RDONLY);      if((strcmp(argv[1],"new"))==0){              for(int i = 2; i < argc; i = i+2){                      int number  = atoi(argv[i+1]);                       //strlen(data) + 1;                      strcpy(data, argv[i]);                      int length = strlen(data) + 1;                      write(fd,&length, sizeof(int));                      write(fd,data, length);                      write(fd,&number, sizeof(int));              }              //close(fd);      }      else{              //}              printf("Not worked");      }      for(int k =0;k < ((argc-2)/2);k++){              int length;              char*name = NULL;              int money;              read(fd, &length, sizeof(int));              name = malloc(length);              read(fd, name, length);              read(fd, &money, sizeof(int));              printf("%10s: %.2f\n", name, money);              }       return 0;         }  

And then here is the output of the binary file

gcc -o gifts board.c  ./gifts new patel 200 Ram 500        : 0.00        : 0.00  od -c gifts.dat  0000000 006  \0  \0  \0   p   a   t   e   l  \0 310  \0  \0  \0 004  \0  0000020  \0  \0   R   a   m  \0 364 001  \0  \0  \0  \0  0000034  

Make sure to use alias gcc='gcc -std=c99'before compiling with gcc

https://stackoverflow.com/questions/66810820/c-program-reading-and-writing-to-binary-files March 26, 2021 at 11:53AM