The first char of my output is omitted in C - c

Question

I can't seem to figure out what is going on with my output. I am reading in multiple lines of user input and outputting corresponding input that exceeds a lower boundary. For some reason when I output, the string that's outputted is omitting the first character of the string. Can anyone tell me why this is occuring?
#include <stdio.h>
typedef struct{
char name[4];
int population;
} state;
enum { MAX_STATES = 10 };
int main()
{
state myStates[MAX_STATES];
int c;
int i = 0;
while ((c = getchar())!= EOF)
{
scanf("%s %d\n", myStates[i].name, &myStates[i].population);
i++;
}
// printf("Last character is [%d]\n", c);
printf("");
if (c <= 0)
{
for(int j = 0; j <= MAX_STATES; j++)
{
if(myStates[j].population >= 10)
printf("%s %d\n", myStates[j].name, myStates[j].population);
else
break;
}
}
return 0;
}
Input:
TX 23
CA 45
Output:
X 23
A 45
Updated Code:
#include <stdio.h>
typedef struct{
char name[4];
int population;
} State;
enum { MAX_STATES = 10 };
int main()
{
State myStates[MAX_STATES];
int i, j;
// Function to read in multiple lines (up to 10) of user input; loop
// controls in place, detects format problems, prevents string buffer
// overflows.
for (i = 0; i < MAX_STATES; i++)
{
if (scanf("%2s %d\n", myStates[i].name, &myStates[i].population) != 2)
break;
}
// Function to output (stdout) array of State structs that exceed 10
// population.
for(j = 0; j < i; j++)
{
if(myStates[j].population >= 10)
printf("%s %d\n", myStates[j].name, myStates[j].population);
else
break;
}
return 0;
}
The output as posted, only goes until there is an input that is less than 10 and it breaks out of the loop. When I didn't have that break statement, I was getting garbage output at the last line. Any suggestions to improve the output?

Answer 1

Replace:
int i = 0;
while ((c = getchar()) != EOF)
{
scanf("%s %d\n", myStates[i].name, &myStates[i].population);
i++;
}
with:
int i;
for (i = 0; i < MAX_STATES; i++)
{
if (scanf("%3s %d", myStates[i].name, &myStates[i].population) != 2)
break;
}
This protects you against entering too many states, uses the for loop to put the loop controls in place, detects format problems, prevents string buffer overflows, and reads the first character into the name. Also, a trailing white space (such as a blank or newline) in a format string is a very bad idea in a scanf() format string if the input is being entered interactively. If the input comes from a file, it is less serious but still unnecessary most of the time. (See Trailing blank in scanf() format for more information.)
Keeping a while loop
If you're really adamant that you need a while loop, then you can use:
int i = 0;
while (i < MAX_STATES && (c = getchar()) != EOF)
{
ungetc(c, stdin);
if (scanf("%3s %d", myStates[i].name, &myStates[i].population) != 2)
break;
i++;
}
or:
int i = 0;
while (i < MAX_STATES && (c = getchar()) != EOF)
{
myStates[i].name[0] = c;
if (scanf("%2s %d", &myStates[i].name[1], &myStates[i].population) != 2)
break;
i++;
}
Note that these while loops still maintain both lots of overflow protection — overflowing the main array, and overflowing the name field. Note that one of the two scanf() statements uses %3s and the other %2s; you should be able to explain why. (And yes, the null byte is not counted by scanf(), so you have to use an 'off-by-one' length in the conversion specification.)
There are, no doubt, other techniques that could also be used. However, I think you'll find that the for loop is more nearly idiomatic C.
One alternative that is often sensible is to use fgets() (or POSIX getline() if it is available) to read whole lines, and then sscanf() to parse the lines. This often leads to more resilient programs, and better error reporting. It also stops people who try to put the information for all 50 states on a single line, or who put each datum on a separate line with a blank line in between them all, from getting away with the malformed data. You can quietly insist on two fields (and, if you're careful, only two fields) on the line.
And the output code?
May I inquire about a suggestion for displaying the output properly?
You have:
printf("");
if (c <= 0)
{
for(int j = 0; j <= MAX_STATES; j++)
{
if(myStates[j].population >= 10)
printf("%s %d\n", myStates[j].name, myStates[j].population);
else
break;
}
}
The first printf() does nothing; it should go. The if (c <= 0) condition is a bit dubious. It is possible to type a null byte (often Control-# or Control-Shift-2), though it would be a bit hard to get that to break the original loop. The for loop should be more like for (int j = 0; j < MAX_STATES; j++) — this is the template for safe for loops in C. You most frequently use for (int i = 0; i < MAX; i++). However, you only want to print the states that were read, so instead of using MAX_STATES, you need to use i as the limit. If you really only want to print the top 9 states (CA, TX, FL, NY, IL, PA, OH, GA, NC — see Wikipedia; Michigan is just shy of 10M, it says), then the if condition is fine.
So, you could use (noting that the input loop sets i to the number of states read successfully):
for (int j = 0; j < i; j++)
printf("State: %.2s, Pop'n: %dM\n", myStates[j].name, myStates[j].population);
You can tweak the format to suit your requirements, of course. This will print nothing if no states were read, or the number of states that were read. If you really want to apply the condition on the population, then you'd use:
for (int j = 0; j < i; j++)
{
if (myStates[i].population >= 10)
printf("State: %.2s, Pop'n: %dM\n", myStates[j].name, myStates[j].population);
}

Answer 2

An alternative is:
int i = 0;
char temp[100];
for(i=0; i<MAX_STATES; i++){
fgets(temp, 100, stdin);
if(strcmp(temp, "\n") == 0)
break;
sscanf(temp, "%s %d\n", myStates[i].name, &myStates[i].population);
}

Answer 3

You could try adding a space before %s in scanf, or specify a strict number of chars.
scanf(" %3s",
Or even use as in Beej's guide:
// read all whitespace, then store all characters up to a newline
scanf(" %[^\n]", s);

Answer 4

You could try adding a space before %s in scanf, or specify a strict number of chars.
Or even use this:
// read all whitespace, then store all characters up to a newline
scanf(" %[^\n]", s);