Print the last error message from stderr?

Question

I created a script to measure distances between villages in the game Travian My code works correctly, but only with a specific partition. Because there is a fifth element with ($X1, $Y1, $X2, $Y2) which is the size of the map

Example: if all ($X1,$Y1,$X2,$Y2) numbers Less than 100 like ( 99 , 1 , -85 , -55 , 0 , 13 ... etc ) AND the map size is 200 (Max 200,-200) It works properly ..

This is the code:

<?php
$distance    =  round(sqrt(pow(bcsub($X1, $X2,1),2)+pow(bcsub($Y1,$Y2,1),2)),1) ;
?>

==the result of==
$X1 = 66
$Y1 = 55
$X2 = 44
$Y2 = 33
is (31.1)

But if the map size is 200 (Max 200,-200) and :-

• I choose a number greater than 100
• one of the numbers is negative

the result will be not correct

==the result of==
$X1 = 101
$Y1 = 160
$X2 = 190
$Y2 = -194
is (365)
And the correct one is (100.6)

http://travian.kirilloid.ru/distance.php#cc=101,160,190,-194&srv=1.45&size=200&spd=7&art=1

the point at (199, 199) is adjacent to (-199, -199) .. and the distance Between them is (4.2) .. in my code Gives me (562.9) ...

How do I solve this problem please :(

Solution

If a program alone does write to stderr you should be able to see its error output without the need for that helper function. In your post your command suggests you didn't use any redirection so you were supposed to see the error stream. To troubleshoot you of course could redirect both stdout and stderr to two separate files, (or both to the same one with &> file.txt ) and see what is going on actually

Comments

[Charlie]

script.sh 2>error; tail -n 1 error; rm -f error; ? First redirecting errors to a file, then getting last line from that file, then deleting file.

[PHP Guru]

I seem to remember this from basic algebra: a²+b²=c². In other words if you know x (the horizontal) and y (the vertical) you can compute the hypotenuse which is the distance between them. square root (x²+y²)=hypotenuse

[Oliver M Grech]

@PHP Guru: That's Pythagoras theorem. For this formula to work, angle of the shortest sides need to be 90 degrees

[Oliver M Grech]

What is the size of the map when your formula is correct?

[PHP Guru]

I assume the map is 2 dimensional? If it's round like the earth then it will not work. If it's 2 dimensional then you can operate on a cartesian coordinate system of x and y and pythagorean theorem works just fine.

[xrescom]

the point at (199, 199) is adjacent to (-199, -199) .. and the distance Between them is (4.2) .. in my code Gives me (562.9) ...

[xrescom]

Thank you, thank you, thank you ... the code works perfectly .