CODEWITHSUNDEEP
c
Jeremy
Jeremy

Reputation: 21

some fgets cannot work in C programming

#include <stdio.h>
#include <string.h>

int main()
{
    int sel_1, sel_2, telno[12], price = 0, sum = 0, i;
    char pkg[2], name[10], addrs[30], name_1[50][50], addrs_1[50][50];

    printf(" Lunch4You Enterprise\n Delivery Service Subscription System\n");
    printf("==========================================================================");
    printf("\nPackage that we have:\n 1. Package A: 20days/month(5days/week) - RM60/month");
    printf("\n 2. Package B: 12days/month(3days/week) - RM45/month");
    printf("\n 3. Package C: 8days/month(2days/week) - RM35/month");

    do
    {
        printf("\nPlease select the package: ");
        scanf("%d", &sel_1);
    }
    while (sel_1 != 1 && sel_1 != 2 && sel_1 != 3);

    switch (sel_1)
    {
        case 1: strcpy(pkg, "A"); price = 60;
                break;
        case 2: strcpy(pkg, "B"); price = 45;
                break;
        case 3: strcpy(pkg, "C"); price = 35;
                break;
    }

    printf("\n\nYou have selected Package %s.", pkg);

    do
    {
        printf("\nHow many receiver of lunchbox?: ");
        scanf("%d", &sel_2);
    }
    while (sel_2 > 5 || sel_2 < 1);

    sum = sel_2 * price;
    printf("\n\nPlease enter the information below:\nName of subscriber: ");
    scanf("%s", &name);
    printf("\nAddress (Pick-up): ");
    fgets(addrs,30,stdin);

    for (i = 0; i < sel_2; ++i)
    {
        printf("Name of receiver (%d): ", i + 1);
        fgets(name_1[i], 50, stdin);
        printf("Address(Receiver)(%d): ", i + 1);
        fgets(addrs_1[i], 50, stdin);
        printf("Tel No (%d)", i + 1);
        scanf("%d", &telno[i]);
    }

    printf("\n\nYour information for lunchbox delivery are:");
    printf("\nPackage : %s", pkg);
    printf("\nPick-up Address: %s", addrs);

    for (i = 0; i < sel_2; ++i)
    {
        printf("\nReceiver %d: %s, %s\n\t\t%d", i + 1, name_1[i], addrs_1[i], telno[i]);
    }
    printf("\n\nTotal fee: RM%d\n", sum);

    return 0;
}

$some fgets cannot work, it just skip to the next fgets then wait for users to enter.(in this case, the fgets(addrs) and fgets(name_1) in the 'for loop' cannot work) can I know why and how to solve this problem? thks.

Upvotes: 0

Views: 95

Answers (2)

Jonathan Leffler
Jonathan Leffler

Reputation: 755064

This sequence is a problem:

scanf("%s", &name);
printf("\nAddress (Pick-up): ");
fgets(addrs,30,stdin);

The scanf() stopped at the first white space character, quite probably a newline; the fgets() then reads up to and including the newline, so it doesn't need to wait for any input because there's a newline already in the input buffer, left over from the scanf() call.

You need to read up to the newline after the scanf(). And you should be checking for problems after each input operation.

if (scanf("%s", name) != 1)
    …report error…
while ((c = getchar()) != EOF && c != '\n')
    ;
if (fgets(addrs, sizeof(addrs), stdin) == 0)
    …report error…

Upvotes: 3

Basile Starynkevitch
Basile Starynkevitch

Reputation: 1

You need to end (not start) your printf(3) format string with \n or to call fflush(3) since stdio(3) is usually buffered (see setvbuf(3)...); so add a fflush(NULL); before every call to scanf.

You should also test the return (scanned items) count of scanf(3).

Read also documentation of fgets(3). You may prefer to use getline(3) or even (on systems having it, like Linux) readline(3)

Upvotes: 2

Related Questions