Question

In C. I want to read in the data of a text file into an array of dynamically allocated structs. The file is read as a command-line argument

The text file format is:

<number of classes in this file>

<department name of class 1>:<number of class 1>:<location of class 1>

<department name of class 2>:<number of class 2>:<location of class 2>

...

Assume that no piece of information in the file contains a colon: the colons are only used as separators. Also, assume that there will be no more than 64 classes in the file.

Here is the struct definition you must use to store each class.

#define MAX_DEPARTMENT_LENGTH 8

#define MAX_COURSE_NUMBER_LENGTH 8

#define MAX_COURSE_LOCATION_LENGTH 32

typedef struct class_info {

       char department [MAX_DEPARTMENT_LENGTH];

       char number [MAX_COURSE_NUMBER_LENGTH];

       char location [MAX_COURSE_LOCATION_LENGTH];

} class_info_t;

Again, this is to be done in C and a response as soon as possible would be preferred, Thank You.

Answer 1

The source code is given below:

/*******
readfile.c
*********/

/* header files*/
#include<stdio.h>
#include<stdlib.h>

/* define constants */
#define MAX_DEPARTMENT_LENGTH 8
#define MAX_COURSE_NUMBER_LENGTH 8
#define MAX_COURSE_LOCATION_LENGTH 32
/* structure declaration */
typedef struct class_info {
char department [MAX_DEPARTMENT_LENGTH];
char number [MAX_COURSE_NUMBER_LENGTH];
char location [MAX_COURSE_LOCATION_LENGTH];
} class_info_t;
/* main function */

int main(int argc,char * argv[]) /* argc - to hold count of command line arguments */
{ FILE * fp; /* argv[] - to hold command line arguments. argv[1] holds data file name passed as command line arg*/
class_info_t * ptr; /* pointer to struct type class_info_t declaration */
int i,j,k,n;
char str[80]; /* string buffer to hold string */
if(argc!=2) /* if file name is not passed as command line arguments */
{printf("Please specify input text file name at command line while executing it");
exit(0);
}
else
{ fp=fopen(argv[1],"r"); /* opens file for reading */
fscanf(fp,"%d",&n); /* reads first number from file which is total no of classes */
if(n>64) /* total classes should not be more than 64 */
{
printf("No of classes is more than 64");
exit(0);
}
else if(n<=0) /* total class is not a -ve number or 0 */
{
printf("No of classes can not be -ve or 0");
exit(0);
}
else
{
ptr=(class_info_t *)malloc(sizeof(class_info_t)*n); /* dynamically allocates memory for all the records */
for(i=0;i<n;i++)
{fscanf(fp,"%s",str); /* reads line wise from file */

for(j=0,k=0;str[j]!=':';j++,k++)
ptr[i].department[k]=str[j];/* populates department data */
ptr[i].department[k]='\0';
  
for(++j,k=0;str[j]!=':';j++,k++)
ptr[i].number[k]=str[j];/* populates number data */
ptr[i].number[k]='\0';

for(++j,k=0;str[j]!='\0';j++,k++)
ptr[i].location[k]=str[j]; /* populates location data */
ptr[i].location[k]='\0';   
}
for(i=0;i<n;i++) /* displays all the records */
{
printf("\nDept: %s\t Number:%s\t Location:%s",ptr[i].department,ptr[i].number,ptr[i].location);
}
printf("\n");
}
fclose(fp);/* closes file */
}
return 0;
}

The source code screen shots are also given for indentation reference:

The output screen shot is also given below:

The above output is taken on ubuntu/linux machine.

The data file data.txt contains following data:

5
aaaaa:2334:12ty
bbbbbb:122:5656
ccccc:343:1212
dddd:2234:5343y
eeeee:554:3236