Reading integers from files..

[pmk123]

Hi friends

I am trying to read a list of double float from a txt-file into my c program, i.e. into an double array I have defined in my program.

I have tried using fread( ), but it seems to be able to handle chars only. Is there a way to read integers?

I am happy to join this forum, hope someone can give me a piece of advice.

[Salem]

If the "integers" are in a text file, chances are that it is text

Like you see for example "12345678", you see 8 characters quite easily using any text editor.
The same integer in a binary file would look like a mess with a text editor, and might read 4 bytes as "00 BC 61 4E" using a hex editor.

Use fgets() to read each line, then sscanf() to extract an integer from that line.

[pmk123]

thanx salem..but how to use sscanf()?
can u explain..

[Salem]

scanf("%d",&myint);
Reads characters from stdin

sscanf( buffer, "%d", &myint );
Reads characters from buffer

The advantage being that if the input is bad in any way, you can simply throw the line away by calling fgets() again. Cleaning up stdin is quite messy.

[pmk123]

should i also create a buffer now...

and one more thing...
in my data.txt file i have 36 integers in a line...
i have to read each integer and assign a variable to it...i.e., how to extract each integer..?

can u please help me...

[swoopy]

      if (sscanf(buf,"%d", &num) != 1)
      {
         printf("Error reading number.\n");
      }
      printf("%d\n", num);

Now put that in a for-loop and change num to be an array and read into &num[i].

[Salem]

> in my data.txt file i have 36 integers in a line...
strtol() returns an integer conversion, and also a pointer to where it got to in the buffer.
You can use this to work your way along the string.

You can achieve the same effect using sscanf with the %n conversion.

[pmk123]

thanx salem..

but can u explain me with its implementation...

[pmk123]

@swoopy

theres an error in ur code..
cannot convert int * to const char *

[swoopy]

>cannot convert int * to const char *
As Salem said, you call fgets to read in a line, then call sscanf. buf should be the char array returned from fgets:

char buf[500];

[pmk123]

@swoopy


then how can i convert the characters in my buffer to the numeric integer array(num[i])...
pls help me out

[pmk123]

please help me out..
as i said i have a data.txt file which contains 36 double floats in a line....
i have to read them from the file and assign a variable name for each of the double float number...


please..do help me out..

[swoopy]

>then how can i convert the characters in my buffer to the numeric integer array(num[i])...
Quoting what I said earlier:
Now put that in a for-loop and change num to be an array and read into &num[i].

[swoopy]

>as i said i have a data.txt file which contains 36 double floats in a line....
The titile of this thread is: Reading integers from files..

To read doubles, change the format specifier given to sscanf to %lf

[pmk123]

this is what i have done...

my datafull.txt contains;
1.11111 2.111111 3.11111111 4.1111111111 5.1111111 6.1111111 7.1111111111 8.1111111111 9.11111111 10.11111111111 11.1111111 12.11111111 13.111111 14.1111111 16.11111111 17.1111111111 18.111111111 19.111111111 20.111111111 21.1111111 22.1111111 23.111111 24.1111111 25.1111111 26.1111111111 27.11111111 28.111111111111 29.11111111 30. 1111111 31.1111111 32.111111111 33.1111111111 34.11111111 35.111111111 36.11111111(end of first line)
1.2222222 2.22222 3.22222 4.2222 .22222 6.22222 7.222222 8.22222 9.2222 10.22222 11.222222 12.2222222 13.22222 14.2222222 15.222222 16.22222 17.222222222 18.2222222222 19.222222222 20.22222222222 21.22222 22.22222 23.22222 24.22222 25.2222 26.2222 27.22222 28.2222 29.222 30.2222 31.22222 32.2222 33.22222222 34.222222 35.22222 36.222222222(end of second line)
1.3333333 2.33333 3.33333 4.33333 5.3333 6.333 7.3333 8.3333 9.333 10.333333 11.33333 12.3333 13.3333 14.3333 15.3333 16.333 17.3333 18.333 19.333 20.333 21.333 22.3333 23.333 24.3333 25.333 26.3333333 27.33333 28.33333333 29.33333 30.3333 31.333 32.33333 33.3333 34.3333 35.3333 36.333333)end of third line)

#include<stdio.h>
#include<conio.h>
#include<string.h>
int main(void)
{
FILE *fp;
int i;
double num[100];
char buf[100];

clrscr();
fp=fopen("datafull.txt","r");

fseek(fp,0,SEEK_SET);
for(i=0;i<36;i++)
{
if(sscanf(buf,"%lf",&num[i])!=1)

{printf("Error");  }
printf("%lf\n" ,num[i]);}

fclose(fp);
getch();
return 0;
}