Thread: Another character input problem

  1. #1
    Registered User
    Join Date
    Nov 2009

    Another character input problem

    Hi. Here's the code:

    /*	Jack White 090455775
    	EE Programming Fundamentals Lab 9
    	Question 3
    #include <stdio.h>
    struct town_info {
        char name[59];   /*The longest place name in Britain is 58 characters long*/
        int d_from_lon;
    int main(void) {
        struct town_info town[5];
        int counter;
        for (counter=0; counter < 5; counter ++) {
            printf("Enter a town: ");
            printf("Enter its distance from London (in miles): ");
            scanf(" %d", &town[counter].d_from_lon);
        printf("\nThe following towns are less than 100 miles from London: \n");
        for (counter=0; counter < 5; counter ++) {
            if (town[counter].d_from_lon < 100) {
        return 0;
    /*End of programme*/
    When it prints out the names at the end, the first character is missing from the first town. I already know about the problem with gets, btw, but I don't want to upset my lecturer. It doesn't work any better with fgets, or indeed scanf.

    Any ideas?


  2. #2
    spurious conceit MK27's Avatar
    Join Date
    Jul 2008
    segmentation fault
    Okay, when I run this, I don't even get that far:

    Enter a town: one
    Enter its distance from London (in miles): 5
    Enter a town: Enter its distance from London (in miles):

    Another "stray newline in the stdin buffer" problem, which is what I would expect.

    Read this:
    STDIN pitfalls
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
    The C Book -- nice online learner guide
    Current ISO draft standard
    CCAN -- new CPAN like open source library repository
    3 (different) GNU debugger tutorials: #1 -- #2 -- #3
    cpwiki -- our wiki on sourceforge

  3. #3
    Registered User slingerland3g's Avatar
    Join Date
    Jan 2008
    Use fgets() instead of gets() because of potential buffer overflow. Also as noted earlier, try the following: (this will not protect you from input that is not expected!)

       scanf("%d%*c", &town[counter].d_from_lon);
    Last edited by slingerland3g; 11-25-2009 at 02:53 PM. Reason: added note on buffer overflow

  4. #4
    Registered User
    Join Date
    Nov 2009
    Cheers! Those pesky buffers.

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