[SOLVED] Trying to take name listings out of file and put into array (complete novice)

abaddon4180 · 12-01-2011, 05:47 PM

Like the title says I am trying to read in a file from the command line and then take the data from that, in the form of,

First Last
First Last
First Last
etc ...

And put it into an array of strings formatted as such,

Last, First
Last, First
Last, First

But I really have no idea where to start. Any help for someone just getting into programming would be appreciated.

David the H. · 12-01-2011, 06:16 PM

Please use [code][/code] tags around your code and data, to preserve formatting and to improve readability.

You may have to explain your requirements in more detail. Are you talking about scripting, some specific programming language, or does it matter which tool you use? And do you only want to reformat each line into "last, first", or do you need the values stored in arrays for other purposes as well? Are you even sure that an array is what you need to use?

The best techniques to use depend a lot on exactly what you're trying to accomplish.

For general bash scripting help, start with these links.

http://mywiki.wooledge.org/BashGuide
http://www.linuxcommand.org/index.php
http://mywiki.wooledge.org/BashFAQ
http://mywiki.wooledge.org/BashPitfalls

And see this page for a rundown on bash's string manipulation features:
http://mywiki.wooledge.org/BashFAQ/100

abaddon4180 · 12-01-2011, 06:32 PM

I need to be able to do some other things once I have the array; sort and search; but I think I can figure that out once I can actually get the array. I just don't know how to go about getting filling the array from the file.

David the H. · 12-01-2011, 06:42 PM

Again, what language? And again, please provide us with some more details on what you want to do. How about showing us an actual example of the input, and how you want the data to be stored/manipulated?

From what you've said so far, it sounds to me like you might need some kind of multi-dimensional array to keep track of each separate entry as well as the individual data fields for them. bash can't do that directly, but it might be possible with linked associative arrays. Other languages might be more suited to the task.

abaddon4180 · 12-01-2011, 06:50 PM

Sorry about that. The language is just C and the input file would look something like,

names.txt

John Smith
Jane Doe
Jane Smith
John Doe
Jake Doe
Jake Smith

While the array has to look like,

Smith, John
Doe, Jane
Smith, Jane
etc ...

I think what I would have to do is individually read the characters from the file and copy them into the row of the array until I reach a new line and then go to the next index and do so again until I am at the end of the file. I have no idea how to do this, though. Once I have that array I think I could just use strcmp and strcpy to search and sort it, which is all I need to do.

abaddon4180 · 12-01-2011, 06:58 PM

I think this might work but I am not sure, especially when it comes to pointers and such which really confuse me

Code:

int main(int argc, char* argv[])
{
   char list[NAMES][LEN];
   
   if (argc != 2)
   {
      printf("\nWrong amount of command line arguments\n");
      return 0;
   }   
   else
      getArray(&argv[1], list);
}

void getArray(char* argv[], char list[][LEN])
{
   int i;
   FILE* fpIn;
   int cInput;
   
   fpIn = fopen(argv[1], "r");

      for (i = 0; i < NAMES; i++)
      {
      while((cInput = fgetc(fpIn)) != 10)
        * list[i] = putchar(cInput);
      }
   fclose(fpIn);
}

abaddon4180 · 12-01-2011, 07:32 PM

Just spent the last half hour typing this up and I know there are a lot of problems.

Code:

#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#define LEN 50
#define NAMES 10

//function declarions

bool menu(char list[][]);
void printArray(char list[][]);
void sortArray(char list[][]);
void searchArray(char list[][]);

int main(int argc, char* argv[])
{
   char list[NAMES][LEN];
   FILE* fpIn;
   int i;
   int cInput;
   
   if (argc != 2)
      printf("\nWrong amount of command line arguments\n");
   else if (!(fpIn = fopen(argv[1], "r")))
      printf("\nFile can't open");
   else
   {   
      for (i = 0; i < NAMES; i++)
      {
      while((cInput = fgetc(fpIn)) != 10)
         *list[i] = cInput;
      }
      menu(list);
   }
   
   fclose(fpIn);

   return 0;
}

bool menu(char list[][LEN])
{
   int userInput;
   bool endMenu = true;

   printf("\nPlease enter one of the following options: ");
   printf("\n   1: Sort in ascending ASCII order by last name");
   printf("\n   2: Search for a particular name");
   printf("\n   3: Print the collection of names");
   printf("\n   4: Quit\n\n");

   scanf("%d", userInput);
   if (userInput == 1)
   {
      sortArray(list);
      printArray(list);
      menu(list);
   }
   else if (userInput == 2)
   {
      searchArray(list);
      menu(list);      
   }
   else if (userInput == 3)
   {
      printArray(list);
      menu(list);
   }
   else if (userInput == 4)
      endMenu = false;
   else
      menu(list);

   return endMenu;
}

void printArray(char list[][LEN]) 
{
   int i;
 
   for (i = 0; i < NAMES; i++)
      printf("\n%s", list[i]); 
}

void searchArray(char list[][LEN])
{
   int i;
   char name[LEN];
   int result = -1;

   printf("\nPlease enter a name to search for: ");
   scanf("%s", name);

   for (i = 0; i < NAMES && result == -1; i++)
      if(strcmp(list[i], name) == 0)
         result = i;
   if(result == -1)
      printf("\nUnable to find name");
   else
      printf("\nName found at position %d in array", i);            
}

void sortArray(char list[][LEN])
{
   char temp[LEN];
   int  i;

   for (i = 0; i < NAMES; i++)
   {
      if(strcmp(list[i], list[i+1]) > 0)
      {
         strcpy(temp, list[i]);
         strcpy(list[i], list[i+1]);
         strcpy(list[i+1], temp);
      }
   } 
}

1. Every time I enter an integer when prompted I get a segmentation fault
2. When I run it without a valid file name in the command prompt I get a segmentation fault
3. I am sure I didn't fill the array correctly, if I filled it at all

abaddon4180 · 12-02-2011, 04:45 AM

Okay. I think I have most of the coding done, besides some formatting of the names, but every time I get to the menu and enter an integer I still get a segmentation fault. I know this is probably something stupid that I am doing, I just don't know what.

Code:

#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#define LEN 50
#define NAMES 10

//function declarions

bool menu(char list[][]);
void printArray(char list[][]);
void sortArray(char list[][]);
void searchArray(char list[][]);

int main(int argc, char* argv[])
{
   char list[NAMES][LEN];
   char name[50];
   FILE* fpIn;
   int i;
   int cInput;
   
   if (argc != 2)
      printf("\nWrong amount of command line arguments\n\n");
   else if (!(fpIn = fopen(argv[1], "r")))
      printf("\nFile can't open\n\n");
   else
   {
      while (!feof(fpIn))
      {         
         fscanf(fpIn, "%s", name);
         strcpy(list[i], name);
         i++;
      }         
      fclose(fpIn);

      menu(list);
   }
     
   return 0;
}

bool menu(char list[][LEN])
{
   int userInput;
   bool endMenu = true;

   printf("\nPlease enter one of the following options: ");
   printf("\n   1: Sort in ascending ASCII order by last name");
   printf("\n   2: Search for a particular name");
   printf("\n   3: Print the collection of names");
   printf("\n   4: Quit\n\n");

   scanf("%d", userInput);
   switch (userInput)
   {
   case 1: sortArray(list);
           printArray(list);
           break;
   case 2: searchArray(list);
           menu(list);
           break;
   case 3: printArray(list);
           menu(list);
           break;
   case 4: endMenu = false;
   default: menu(list);
   }

   return endMenu;
}

void printArray(char list[][LEN]) 
{
   int i;
 
   for (i = 0; i < NAMES; i++)
      printf("\n%s", list[i]); 
}

void searchArray(char list[][LEN])
{
   int i;
   char name[LEN];
   int result = -1;

   printf("\nPlease enter a name to search for: ");
   scanf("%s", name);

   for (i = 0; i < NAMES && result == -1; i++)
      if(strcmp(list[i], name) == 0)
         result = i;
   if(result == -1)
      printf("\nUnable to find name");
   else
      printf("\nName found at position %d in array", i);            
}

void sortArray(char list[][LEN])
{
   char temp[LEN];
   int  i;

   for (i = 0; i < NAMES; i++)
   {
      if(strcmp(list[i], list[i+1]) > 0)
      {
         strcpy(temp, list[i]);
         strcpy(list[i], list[i+1]);
         strcpy(list[i+1], temp);
      }
   } 
}

abaddon4180 · 12-02-2011, 04:58 AM

Never mind. Just realized I was missing the '&' in the scanf in the menu function. Like I said, I am new to programming.