Writing a UNIX shell script to call a C function and redirecting data to a .txt file
Hi, I am complete new to C programming and shell scripting. I just wrote a simple C code to calculate integral using trapezoid rule. I am prompting user to pass me No. of equally spaced points , N , upper and lower limit. My code looks as follows so far:
Code:
#include<stdio.h>
#include<string.h>
#include<math.h>
#include <stdlib.h>
#define PI 3.14159265358979323846
float fn(float x)
{
float integrand;
integrand = (1.0/(1.0+x*x));
return integrand;
}
int main()
{
char str[100000];
int i,N;
float a,b,sum=0,result=0,h;
float error;
printf("Enter the no of equally spaced points as a string =");
scanf("%s", str);
N=atoi(str);
printf("Enter the lower limit=");
scanf("%f",&a);
printf("Enter the upper limit=");
scanf("%f",&b);
h=(b-a)/(N-1);
for(i=1;i<=N;i++)
{
sum=sum+fn(a+i*h);
result=(fn(a)+fn(b)+2*sum)*h/2;
error = fabs((atan(b)-atan(a))-result);
//error = PI/2.0 - result;
printf("N=%d result=%f error=%f\n", i, result, error);
}
printf("final result =%f\n", result);
printf("cumulative error =%f\n", error);
}
Now, I want to write a unix script which calls the program for N = 2^{i} for integers i from 1, 2, 3, ..., 20 and use the Unix redirect operator > to record this data in a file.
I am searching over internet how to pass argument through shell and even how to modify my code so that it reads that passed parameter, still no good answer. Your suggestions are highly appreciated. It will help me learn the unix shell scripting as well.
i have a function written in one shell script and i want to call that function in another shell script and use the value returned by that script.
can any one suggest me how can i do that?
regards,
Rajesh.P (4 Replies)
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Discussion started by: Gurdza32
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LEARN ABOUT ULTRIX
atan2
sin(3m)sin(3m)Name
sin, cos, tan, asin, acos, atan, atan2 - trigonometric functions and their inverses
Syntax
#include <math.h>
double sin(x)
double x;
float fsin(x)
float x;
double cos(x)
double x;
float fcos(x)
float x;
double tan(x)
double x;
float ftan(x)
float x;
double asin(x)
double x;
float fasin(x)
float x;
double acos(x)
double x;
float facos(x)
float x;
double atan(x)
double x;
float fatan(x)
float x;
double atan2(y,x)
double y,x;
float fatan2(y,x)
float y,x;
Description
The and functions return trigonometric functions of radian arguments x for double data types.
The and functions return trigonometric functions for float data types.
The and functions return the arc sine in the range -pi/2 to pi/2 for double and float data types, respectively.
The and functions return the arc cosine in the range 0 to pi for double and float data types, respectively.
The and functions return the arc tangent in the range -pi/2 to pi/2 for double and float data types, respectively.
The and functions return the arc tangent of y/x in the range -pi to using the signs of both arguments to determine the quadrant of the
return value for double and float data types, respectively.
Error (due to roundoff)
When P stands for the number stored in the computer in place of pi = 3.14159 26535 89793 23846 26433 ... . and "trig" stands for one of
"sin", "cos" or "tan", then the expression "trig(x)" in a program actually produces an approximation to trig(x*pi/P), and "atrig(x)"
approximates (P/pi)*atrig(x). The approximations are close.
P differs from pi by a fraction of an ulp; the difference is apparent only if the argument x is huge, and even then the difference is
likely to be swamped by the uncertainty in x. Every trigonometric identity that does not involve pi explicitly is satisfied equally well
regardless of whether P = pi. For example, sin(x)**2+cos(x)**2 = 1 and sin(2x) = 2sin(x)cos(x) to within a few ulps regardless of how big
x is. Therefore, the difference between P and pi is unlikely to effect scientific and engineering computations.
Return Values
All the double functions return NaN if NaN is passed in.
If |x| > 1 then (x) and (x) will return the default quiet NaN.
The function defines (0,0) = NaN.
See Alsohypot(3m), math(3m), sqrt(3m)
RISC sin(3m)
09-22-2016
