problem in a code with filehandling

**Mark McIntyre** · Feb 16 '08, 12:25 PM

Re: problem in a code with filehandling

neha_chhatre@ya hoo.co.in wrote:

i have a wierd problem...iam not able to understand wat is goin
wrong...i have written a code which reads the values form a text file
(it contains lot of values like time=1.147279,v alue=240.66 and so
on............. ...)
the code is workin well for the firs five iterations...bu t thn it isnt
doing the computations properly after the 5th iteration (sumthing is
goin wrong in the if loop)
pls help me out with this
Iam posting the entire code here.......

You didn't tell us what the file contained, or what the actual error
was. Post an example of the input and output, and where you think its wrong.

#include<stdio. h>
#include<stdlib .h>
#include<string .h>
>
int main()
{
FILE *fp;
char ch,str[100],str1[100];
>
int c=0,i,j;
float t=0.0,t1=1.0472 789115646258,t2 =0.0,sum=0.0,av g=0.0,check=0.0 ;

Float is often a bad choice for mathematical work. The precision is
quite poor, and large errors can rapidly creep in.

--
Mark McIntyre

CLC FAQ <http://c-faq.com/>
CLC readme: <http://www.ungerhu.com/jxh/clc.welcome.txt >

**Bartc** · Feb 16 '08, 01:45 PM

Re: problem in a code with filehandling

<neha_chhatre@y ahoo.co.inwrote in message
news:23108ade-0319-4612-b6cf-16ffe2816614@s3 7g2000prg.googl egroups.com...

On Feb 16, 5:17 pm, Mark McIntyre <markmcint...@s pamcop.netwrote :

>neha_chha...@y ahoo.co.in wrote:

i have a wierd problem...iam not able to understand wat is goin
wrong...i have written a code which reads the values form a text file
(it contains lot of values like time=1.147279,v alue=240.66 and so
on............. ...)
the code is workin well for the firs five iterations...bu t thn it isnt
doing the computations properly after the 5th iteration (sumthing is
goin wrong in the if loop)
pls help me out with this
Iam posting the entire code here.......

What exactly is it doing wrong? What should the output be at the sixth
iteration (at points[6] in the file?).
--
Bart

**Ben Bacarisse** · Feb 16 '08, 03:25 PM

Re: problem in a code with filehandling

neha_chhatre@ya hoo.co.in writes:

the code is workin well for the firs five iterations...bu t thn it isnt
doing the computations properly after the 5th iteration (sumthing is
goin wrong in the if loop)

On my system it works with the data you posted elsewhere (as far as I
can tell). What is it that goes wrong?

#include<stdio. h>
#include<stdlib .h>
#include<string .h>
>
int main()
{
FILE *fp;
char ch,str[100],str1[100];
>
int c=0,i,j;
float t=0.0,t1=1.0472 789115646258,t2 =0.0,sum=0.0,av g=0.0,check=0.0 ;
>
fp=fopen("pt1.t xt","rb");
if (fp==NULL)
perror ("Error opening file: pt1.txt");
else
{
while(!feof(fp) )

Not usual the wight way to do input in C. See the FAQ at
http://c-faq.com/ (specifically Q 12.2).

{
>
fscanf (fp, "%s", str);
i=strcmp(str,"t ime");
if(i==0)
{
printf("t1=%f\n ",t1);
fscanf (fp, "%s", str);
fscanf (fp, "%f",&t);
>
>
fscanf (fp, "%s", str);
j=strcmp(str,"v alue");
>
>
if(j==0)
{
fscanf (fp, "%s", str);
fscanf (fp, "%f",&t2);
printf("t2=%f\n ",t2);
}
>
check=t1+0.1;

This is very convoluted. fscanf can tell you if the input looks right
(i.e. has the right fixed strings in it) and can tell you that the
numbers were read and converted correctly. For example:

do {
switch (fscanf(fp, "time = %f value = %f", &t, &v)) {
case 2:
printf("%f %f\n", t, v); /* change this to do what you want */
break;
case 1:
printf("Time not followed by value.\n");
break;
default:
fgetc(fp);
}
} while (!feof(fp));

It relies on allowing fscanf to fail a lot, but unless you need
blistering speed, that won't be a problem.

--
Ben.

**Herbert Rosenau** · Feb 17 '08, 10:25 AM

Re: problem in a code with filehandling

On Sat, 16 Feb 2008 12:02:39 UTC, neha_chhatre@ya hoo.co.in wrote:

i have a wierd problem...iam not able to understand wat is goin
wrong...i have written a code which reads the values form a text file
(it contains lot of values like time=1.147279,v alue=240.66 and so
on............. ...)
the code is workin well for the firs five iterations...bu t thn it isnt
doing the computations properly after the 5th iteration (sumthing is
goin wrong in the if loop)
pls help me out with this
Iam posting the entire code here.......
>
#include<stdio. h>
#include<stdlib .h>
#include<string .h>
>
int main()
{
FILE *fp;
char ch,str[100],str1[100];
>
int c=0,i,j;
float t=0.0,t1=1.0472 789115646258,t2 =0.0,sum=0.0,av g=0.0,check=0.0 ;
>
fp=fopen("pt1.t xt","rb");
if (fp==NULL)
perror ("Error opening file: pt1.txt");
else
{
while(!feof(fp) )

As you have'nt tried to read a single byte from the file the while
will loop on

{
>
fscanf (fp, "%s", str);

As you does NOT test the result of fscanf() you continues into
unspecified behavior when it ends with either EOF oer error, so str
may not changed as you expected

i=strcmp(str,"t ime");
if(i==0)
{
printf("t1=%f\n ",t1);
fscanf (fp, "%s", str);
fscanf (fp, "%f",&t);
>
>
fscanf (fp, "%s", str);

Same as above; no test for EOF or error is done, so any error or EOF
left undedected.

j=strcmp(str,"v alue");
>
>
if(j==0)
{
fscanf (fp, "%s", str);
fscanf (fp, "%f",&t2);

same as above

printf("t2=%f\n ",t2);
}
>
check=t1+0.1;
>
>
printf("t=%f\n" ,t);
printf("check=% f\n",check);
>
if(t==check)
{
>
sum=sum+t2;
c++;
printf("sum=%f\ n",sum);
printf("c=%d\n" ,c);
}
>
else
{
>
printf("sum=%f\ n",sum);
sum=0.0;
printf("c=%d\n" ,c);
c=0;
sum=sum+t2;
c++;
}
>
t1=t;
>
}
}
fclose(fp);
}
>
//printf("%d",c);
}
>

Nobody can tell what wents wrong because you have too many (excactly
more than 0) attempts to read without a test for success.

--
Tschau/Bye
Herbert

Visit http://www.ecomstation.de the home of german eComStation
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problem in a code with filehandling

problem in a code with filehandling

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