Need Help in displaying file contents.

bhullar_v · #1 24-Sep-2005, 21:10

The file that I have has the following format of the customers :-

Customer file format:
<id>,<surname>,<firstname>,<address>,<suburb>,<pos tcode>,
<phone>

Example:
C0001,Bloggs,Joe,123 Long Street,Melbourne,3000,93005555

I could display them in the same format but I want to display them as follewing:-

Example:

ID Surname FirstName Address Suburb Post Phone
----- ------------ -------- --------------------
C0001 Bloggs Joe 123 Long Street Melbourne 3000 93005555
... ... ... ... ... ... ...

I have written some of the structures for this:

CPP / C++ / C Code:

/* Constants for customer information. */
#define CUSTID_LEN 5
#define SURNAME_MAX 12
#define FIRSTNAME_MAX 12
#define ADDRESS_MAX 20
#define SUBURB_MAX 12
#define POSTCODE_LEN 4
#define PHONENUM_LEN 8

typedef struct customerNode* CustomerNodePtr;
typedef struct stockNode* StockNodePtr;

/* Structure definitions. */
typedef struct customerNode
{
   char custID[CUSTID_LEN + 1];
   char surname[SURNAME_MAX + 1];
   char firstName[FIRSTNAME_MAX + 1];
   char address[ADDRESS_MAX + 1];
   char suburb[SUBURB_MAX + 1];
   unsigned postCode;
   unsigned phoneNum;
   CustomerNodePtr nextCust;
} CustomerNodeType;

I would really appreciate anyone who helps me with this one.
Thanks

Guidelines Plz · #2 24-Sep-2005, 21:18

Help with what? You need to post the code you are having trouble with, or at least need help with. There's nothing in your post for us to work with, code-wise. See Guideline #2

L7Sqr · #3 24-Sep-2005, 21:32

Please mention what language you wish to use. What you have is both valid C and valid C++.
Have you tried anything other than the structure of the data (code that is)? Try to implement a small main funtion that reads the lines of the file and simple prints them back out to the screen.
Once this is working, there are many ways to parse strings.
Get that working and we can help you from there.

bhullar_v · #4 24-Sep-2005, 23:05

I have used the following code in order to display the file as it is........but can't display it in the formatted manner.

The code is obviously in C.

The ts.h is just the file I have specified above as structures.

CPP / C++ / C Code:

#include<stdio.h>
#include"ts.h"

int main(void)

{

FILE *fp;

char c;
fp = fopen("customer.csv", "r");
do
putchar(c = getc(fp));
while(c != EOF);
return EXIT_SUCCESS;
}

Thanks.

Paramesh · #5 24-Sep-2005, 23:26

hi,
use fread and fwrite to read and write from a file...
the syntax of fread and fwrite is

CPP / C++ / C Code:

size_t fread( 
   void *buffer,
   size_t size,
   size_t count,
   FILE *stream 
);

size_t fwrite(
   const void *buffer,
   size_t size,
   size_t count,
   FILE *stream 
);

where

buffer
Pointer to data to be written.
size
Item size in bytes.
count
Maximum number of items to be written.
stream
Pointer to FILE structure

for example, if u want to read 5 items of type customernode then the code would be

CPP / C++ / C Code:

FILE *fp;
customernodeptr cptr;
fp = fopen("customer.csv", "r");
fread(cptr,sizeof(cptr),5,fp);

then u can print as required.

WaltP · #6 25-Sep-2005, 01:39

Quote:

Originally Posted by bhullar_v

I have used the following code in order to display the file as it is........but can't display it in the formatted manner.

The code is obviously in C.

The ts.h is just the file I have specified above as structures.

CPP / C++ / C Code:

#include<stdio.h>
#include"ts.h"

int main(void)

{

FILE *fp;

char c;
fp = fopen("customer.csv", "r");
do
putchar(c = getc(fp));
while(c != EOF);
return EXIT_SUCCESS;
}

Thanks.

What 'read/input' commands have you been taught?

You need to read a line of the file (probably using fgets(), it's safest and easiest.
Then you have to split up the line read into your customerNode fields (each with a \0 (NULL) at the end).

Then you can print out each field at will (or on the monitor if you prefer -- it's hard to read Will).

kobi_hikri · #7 25-Sep-2005, 06:32

Below is an example of file reading using fgets.
You have to check that your file was opened succesfully before working with the file, or your application will be terminated faster than a Jedi knight terminates an imperial robot

MAX_LENGTH is just a constant I defined for my application. modify it.
Also, point to the name of your file.

CPP / C++ / C Code:

FILE *ifp;
ifp = fopen(argv[argument_index],"r");
if (ifp)
   {
      char current_line[MAX_LENGTH];
      //File opened successfully.
      while (fgets(current_line,MAX_LENGTH,ifp))
      {
      //Do whatever you want to do with your record
      }
   }

Best regards,
Kobi Hikri.

davekw7x · #8 25-Sep-2005, 09:04

Quote:

Originally Posted by Paramesh

use fread and fwrite to read and write from a file...

Here is his typical line from the input file. Since the actual sizes of customer name fields, address field, etc. are not known, I can't see any practical reason to use fread to get the information.

Code:

C0001,Bloggs,Joe,123 Long Street,Melbourne,3000,93005555

Quote:

Originally Posted by Paramesh

for example, if u want to read 5 items of type customernode then the code would be

CPP / C++ / C Code:

FILE *fp;
customernodeptr cptr;
fp = fopen("customer.csv", "r");
fread(cptr,sizeof(cptr),5,fp);

Sorry, Not Even Close, for Several Big Reasons:

CPP / C++ / C Code:

#include <stdio.h>
/* Constants for customer information. */
#define CUSTID_LEN 5
#define SURNAME_MAX 12
#define FIRSTNAME_MAX 12
#define ADDRESS_MAX 20
#define SUBURB_MAX 12
#define POSTCODE_LEN 4
#define PHONENUM_LEN 8

typedef struct customerNode* CustomerNodePtr;
typedef struct stockNode* StockNodePtr;

/* Structure definitions. */
typedef struct customerNode
{
   char custID[CUSTID_LEN + 1];
   char surname[SURNAME_MAX + 1];
   char firstName[FIRSTNAME_MAX + 1];
   char address[ADDRESS_MAX + 1];
   char suburb[SUBURB_MAX + 1];
   unsigned postCode;
   unsigned phoneNum;
   CustomerNodePtr nextCust;
} CustomerNodeType;

int main()
{
  FILE *fp;
  CustomerNodePtr cptr;
  printf("sizeof(cptr) = %d\n", sizeof(cptr));

  //fp = fopen("customer.csv", "r");
  //fread(cptr,sizeof(cptr),5,fp); <<== don't do this: it's disaster waiting to happen!!!!!!!!

  printf("Number of bytes that would have been read = %d\n", 5 * sizeof(cptr));
  printf("1. Does that seem right?\n");
  printf("2. Where would they have been put???\n");
  return 0;
}

My output:

Quote:

sizeof(cptr) = 4
Number of bytes that would have been read = 20
1. Does that seem right?
2. Where would they have been put???

Regards,

Dave

kobi_hikri · #9 25-Sep-2005, 09:14

Quote:

Originally Posted by davekw7x

Here is his typical line from the input file. Since the actual sizes of customer name fields, address field, etc. are not known, I can't see any practical reason to use fread to get the information.

Hey Dave.

Could you please explain this point ?
I usually use fgets and strtok to read and decompose lines from a file, but fgets is also being bounded by an upper bound ...
Is there away to read lines without an upper bound ? I mean, I do need to declare a fixed size buffer before reading into it (or not ?).

Kobi Hikri.

davekw7x · #10 25-Sep-2005, 10:22

Quote:

Originally Posted by kobi_hikri

Hey Dave.

Could you please explain this point ?
I usually use fgets and strtok to read and decompose lines from a file, but fgets is also being bounded by an upper bound ...
Is there away to read lines without an upper bound ? I mean, I do need to declare a fixed size buffer before reading into it (or not ?).

Kobi Hikri.

The answer to that question is: "it depends".

In order to use fread(), you have to know exactly how many bytes to read. This is sometimes useful if your input fields always have an exact, known length.

Take the surname field: its buffer size is 13 (max length of the name is 12 chars + one char required for the terminating '\0'). The input line given in the example has a surname that was six chars long.

If you use fread() to read the number of bytes in the given struct, they won't end up in the proper fields. Unless, that is, you make sure that the files were written with all fields padded out to the correct length (with leading zeros for numeric fields and trailing blanks for character fields, for example.) This was not the case for the example input line given by the Original Poster. Therefore my comment that I don't think it's very practical to use fread() for this kind of data base. Possible? yes. Practical? no. (Well, that's my opinion anyhow.)

For C++ programs, getline with a std::string allows inputs up to the limits of memory in your system (Actually, probably limited to a few gigabytes in 32-bit systems.)

For C programs, you could use fgets() into a buffer of size BUFSIZ (defined in <stdio.h> The value of BUFSIZ is implementation-dependent, and there is even a function that you can use to make it whatever value you want. I'll leave it up to you to find it --- I personally have never found a reason to change the size of stream I/O buffers but ...

(You can investigate properties and implications of BUFSIZ if you are really interested.)

If the user input line is greater than or equal to BUFSIZ, then the input line will not have a '\n' char (it is always terminated by a \'0') so you can detect and and you may be able to handle such extremenly long cases, if you need to.

I have found that some compilers have functions that simply stop accepting characters if more than BUFSIZ-1 are entered on a given input line, and others apparently have an even larger buffer somewhere that keeps on storing additional chars, so if your program does encounter a case of extremely long input lines, recovery of lost input may or may not be possible.

CPP / C++ / C Code:

#include <stdio.h>
#include <string.h>
int main()
{
  char inbuf[BUFSIZ];
  printf("BUFSIZ = %d\n", BUFSIZ);
  printf("Hold some key down until at least %d chars have been echoed to the screen:\n", BUFSIZ);
  fgets(inbuf, BUFSIZ, stdin);
  printf("1: strlen(inbuf) = %d\n", strlen(inbuf));
  printf("If you held the key for more than %d chars, what happened to the rest?\n", BUFSIZ-1);
  printf("If your system is now waiting for input, the extra chars are gone, gone, gone!\n");
  fgets(inbuf, BUFSIZ, stdin);
  printf("2: strlen(inbuf) = %d\n", strlen(inbuf));

  return 0;
}

I ran this program (Borland compiler) and camped on the 'a' key until it stopped echoing 'a' to the screen.

Quote:

BUFSIZ = 512
Hold some key down until at least 512 chars have been echoed to the screen:

aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
I got several rows of 'a's here, then it stopped echoing. I released the 'a' key and pressed 'Enter'. Here's what it showed me:

Quote:

1: strlen(inbuf) = 511
If you held the key for more than 511 chars, what happened to the rest?
If your system is now waiting for input, the extra chars are gone, gone, gone!

The system was waiting for more input, so I typed Bye, and here's what it said:

Quote:

2: strlen(inbuf) = 4

Now, with the same program, compiled with Microsoft Visual C++ here's the result:

Quote:

BUFSIZ = 512
Hold some key down until at least 512 chars have been echoed to the screen:

...
Here I held the 'a' key down for about seven complete rows (80 columns per row) on my console window. It never stopped echoing chars, so I released the key and pressed 'Enter'. Then all of the following spilled out (didn't wait for additional characters)
...

Quote:

1: strlen(inbuf) = 511
If you held the key for more than 511 chars, what happened to the rest?
If your system is now waiting for input, the extra chars are gone, gone, gone!
2: strlen(inbuf) = 50

gcc did the same, except BUFSIZ was shown to be 1024 instead of 512.

So, if you have really long lines of input and you want to use fgets and you want to make sure that you don't drop any chars, you have a problem. Then, maybe you have to use fread to read smaller chunks and process the input accordingly. (Using combinations of sscanf, strtok, etc.) Or, as in the case of encryption/decryption, read one char at a time (using getchar()) into an internal buffer and process the chars or blocks of chars as they appear.

In cases like the example of the Original Post, any really long input lines (longer than the size of the struct) are an indication of a bad data base, and programs like this typically just report an error (giving the line number), and expect the user to resort to some other program or method (manual inspection of the file) to recover.

Regards,

Dave

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