looping and condition problems

This is a discussion on looping and condition problems within the C Programming forums, part of the General Programming Boards category; Hi I need to a program which prompt for how many names the user will enter Then a (dynamic) array ...

  1. #1
    Registered User
    Join Date
    Mar 2008
    Posts
    9

    Question looping and condition problems

    Hi
    I need to a program which prompt for how many names the user will enter
    Then a (dynamic) array of the requested size is created. It is an array of strings.
    In a loop of the requested size
    prompt the user to enter a name of at most 20 characters.
    read the name and turn into a string.
    allocate memory for a copy of the string and store its address in the appropriate item of the dynamic array.
    copy the input string into the memory allocated.
    When the loop is over, display the strings stored in the dynamic array.

    problems:
    1. i cant show " empty input" for the user to enter only "\n"
    2. the loop cant run properly, it always trapped after i enter all the names

    this is the work i done so far.
    Thank you for the effort!

    Code:
    #include <stdio.h>
    #include <string.h>
    #include <stdlib.h>
    
    #define merror()   {printf("memory allocation problem\n");exit(1);}
    
    int main(void)
    {
    int num;
    char p;
    char **resp;
    char buf[21];
    int i, j;
    
    	printf(" how many names will be entered : \n");
    	fflush(stdout);
        scanf("%d", &num);
    	fflush(stdin);
    
    	if (num ==0)
    		{
    		printf(" empty input \n");
    		}
    	else if (num>= 10)
    		{
    		printf(" input too long \n");
    		}
    	else if (num >0 && num<10)
    		{
    		printf("you will enter %d names \n", num);
    		}
    
    for(i=0; i < num; i++)
    {
    	printf(" enter the name \n");
            for(j=0; j<21; j++) 
            {
    	      buf[j]=fgetc(stdin);
    	      if (buf[j]=='\n')
    	      {
    	        buf[j]='\0';
    	        break;
    	      }
    	    }
    
    	    if (j==21)
    	    {
    	      printf("input too long\n");
    	      while(fgetc(stdin)!='\n');
    	      continue;
    	    }
    }
    
    for(i=0; i< num; i++)
        {
        for(j=0; j<21; j++)
         {
        **resp= buf[j];
         }
     }
    
      printf("\names as entered: \n");
      for(i=0; i<num; i++)
      {
        printf("%s\n",**resp);
      }
    
    return 0;
    }

  2. #2
    CSharpener vart's Avatar
    Join Date
    Oct 2006
    Location
    Rishon LeZion, Israel
    Posts
    6,484
    1.
    i cant show " empty input" for the user to enter only "\n"
    Read the input with fgets - then analyze it with strtol
    There are several samples on the forum

    2. fflush(stdin); is not defined - read FAQ


    3. **resp you dereference uninitialized pointer

    4. In your input loop you always oerwrite same buffer - loosing all inputs except the last


    5.
    Code:
    for(i=0; i<num; i++)
      {
        printf("&#37;s\n",**resp);
      }
    Do you see i somewhere inside the loop?
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

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