How do I concatenate strings to generate fixed width output - c

Question

I have an array of structures, where each structure contains a first name and a last name, along with other information. I'm trying to print the array in tabular form, something like this
+---------------------------+--------+--------+
| Student Name | Test 1 | Test 2 |
+---------------------------+--------+--------+
| Pousseur, Henri | 95 | 92 |
| Boyer, Charles | 90 | 97 |
+---------------------------+--------+--------+
However, my output looks like this
+---------------------------+--------+--------+
| Student Name | Test 1 | Test 2 |
+---------------------------+--------+--------+
| Pousseur, Henri | 95 | 92 |
| Boyer, Charles | 90 | 97 |
+---------------------------+--------+--------+
My question is, how do I concatenate the last name to the first name (with a comma in between), and then print the whole thing as a fixed width string? So that my table lines up correctly.
Here's my code:
#include <stdio.h>
#define NAME_LEN 25
typedef struct
{
char fname[NAME_LEN+1];
char lname[NAME_LEN+1];
int score1;
int score2;
} STUREC;
void printRecords(STUREC records[], int count)
{
printf("+---------------------------+--------+--------+\n");
printf("| Student Name | Test 1 | Test 2 |\n");
printf("+---------------------------+--------+--------+\n");
for (int i = 0; i < count; i++)
printf ("| %-s, %-26s| %4d | %4d |\n", records[i].lname, records[i].fname, records[i].score1, records[i].score2 );
printf("+---------------------------+--------+--------+\n");
}
int main(void)
{
STUREC records[] = {
{ "Henri" , "Pousseur", 95, 92 },
{ "Charles", "Boyer" , 90, 97 }
};
printRecords(records, 2);
}

Answer 1

Note that printf returns the number of characters printed. So if you want to print the name within a fixed width, you can print the name, and then output spaces as needed to fill the width.
#define WIDTH 26
int count = printf( "%s, %s", records[i].lname, records[i].fname );
if ( count < WIDTH )
printf( "%*s", WIDTH-count, "" );
In the format string "%*s", the * tells printf that the width of the string will be passed as an argument. The WIDTH-count argument is the number of spaces that need to be printed, and "" is just an empty string. So for example, if count is 16, then WIDTH-count is 10, so the printf is equivalent to
printf( "%10s", "" );
which will print 10 spaces.

Answer 2

This is just an adpatation of #user3386109 answer.
Add
#define WIDTH 27 // You get a max width of 26
somewhere in the beginning of your program and a string
char fullname[WIDTH];
somewhere in the beginning of the main.
Then make changes like below :
printf("\n+---------------------------+--------+--------+--------+--------+--------+--------+---------+-------+\n");
printf("| Student Name | ID | Test 1 | Test 2 | Proj 1 | Proj 2 | Proj 3 | Average | Grade |\n");
printf("+---------------------------+--------+--------+--------+--------+--------+--------+---------+-------+\n");
for (i = 0; i < count; i++)
{
int lname_len=strlen(records[i].lname);
int fname_len=strlen(records[i].fname);
snprintf(fullname,WIDTH,"%s,%s%*s", records[i].lname,records[i].fname,(WIDTH>(lname_len+fname_len)?(WIDTH-(lname_len+fname_len)):0),"");
/* The above step concatenates - since you're very interested in it -
* the sirname and the first name into a string fullname making sure
* that the string is padded to 26 characters utmost.
*/
printf ("| %s | %-7.6d| %4d | %4d | %4d | %4d | %4d | %6.2f | %-2s |\n", fullname, records[i].id, records[i].score1,
records[i].score2, records[i].score3, records[i].score4, records[i].score5,
records[i].ave, records[i].grade);
}
printf("+---------------------------+--------+--------+--------+--------+--------+--------+---------+-------+\n");
printf("\nHave A Terrible Day!\n\n");
Note the ternary expression :
(WIDTH>(lname_len+fname_len)?(WIDTH-(lname_len+fname_len)):0)
in snprintf. This will be evaluated to unused width, if any which we pad with emptry strings "" or null characters.
If you didn't understand it please have a look here