Visit Our UNIX and Linux User Community

Maths with variables

Thread Tools Search this Thread
Top Forums Shell Programming and Scripting Maths with variables
# 1  
Old 01-19-2010
Maths with variables

I'm trying to write a while loop for a decimal value in tcsh which I know can't be done. Instead I want my increments to be one order of magnitude too large and then divide it by 10 when I use the variable. However, I don't know how to divide my variable and set it as another.

set RI_min = 10
set RI_max = 30
set RI_inc = 1

# Run Flex2d for each RI
set RI = $RI_min
echo "Calculating flexure for:"
while ($RI <= $RI_max)

@ RI = $RI + $RI_inc

I then want to set PI to equal RI/10 to use PI in another program so my PI values will range from 1.0 to 3.0.

Last edited by Scott; 01-19-2010 at 11:48 AM.. Reason: Please use code tags
# 2  
Old 01-19-2010
The bc(1) command can do scripted mathematics for you, e.g.:

$ RI=30
$ RESULT=`echo "scale=3; 10 / ${RI}" | bc`
$ echo $RESULT

The above will work in BASH, Bourne and Korn shell.

So the script in Bourne would be:

# Run Flex2d for each RI
echo "Calculating flexure for:"
while [ ${RI} -le ${RI_max} ]; do
  RI=`expr ${RI} + ${RI_inc}`
  PI=`echo "scale=3; 10 / ${RI}" | bc`
  echo PI = ${PI}

and running this produces:
Calculating flexure for:
PI = .909
PI = .833
PI = .769
PI = .714
PI = .666
PI = .625
PI = .588
PI = .555
PI = .526
PI = .500
PI = .476
PI = .454
PI = .434
PI = .416
PI = .400
PI = .384
PI = .370
PI = .357
PI = .344
PI = .333
PI = .322

I'll leave you to translate it into tcsh if you must.

This site:
Math Commands
goes into more detail about calculations in scripts.

Previous Thread | Next Thread
Test Your Knowledge in Computers #681
Difficulty: Medium
In 2011, the Solaris 11 kernel source code was leaked to WikiLeaks.
True or False?

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Calculate the constant e to 14+ decimal places using integer maths.

Hi guys... I am loving this integer maths thing. 64 bit systems are certainly easier than 32 bit, but hey, I don't intend to leave out my fav' platform. Using one of the 'Brothers' methods, URL inside the code. #!/bin/sh # # #!/usr/local/bin/dash # # Brother's formula . #... (2 Replies)
Discussion started by: wisecracker
2 Replies

2. Shell Programming and Scripting

Passing awk variables to bash variables

Trying to do so echo "111:222:333" |awk -F: '{system("export TESTO=" $2)}'But it doesn't work (2 Replies)
Discussion started by: urello
2 Replies

3. Shell Programming and Scripting

BASH arrays and variables of variables in C++

Sometimes it is handy to protect long scripts in C++. The following syntax works fine for simple commands: #define SHELLSCRIPT1 "\ #/bin/bash \n\ echo \"hello\" \n\ " int main () { cout <<system(SHELLSCRIPT1); return 0; } Unfortunately for there are problems for: 1d arrays:... (10 Replies)
Discussion started by: frad
10 Replies

4. Shell Programming and Scripting

Running a script with multiple variables like 25 variables.

Hi All, i have a requirement where i have to run a script with at least 25 arguements and position of arguements can also change. the unapropriate way is like below. can we achieve this in more good and precise way?? #!/bin/ksh ##script is sample.ksh age=$1 gender=$2 class=$3 . . .... (3 Replies)
Discussion started by: Lakshman_Gupta
3 Replies

5. Shell Programming and Scripting

Maths in shell scripts

Hi, Need help on this. I need to increment a variable by 1 but retain as 2 characters. I am using expr to do additions: NEWSERIAL=`expr $SERIAL + 1` $SERIAL can range from 01-99. After adding "1", I need the result to be 2 characters, eg: 02+1 = 03. By default expr will truncate the... (4 Replies)
Discussion started by: vchee
4 Replies

6. Shell Programming and Scripting

Simple maths calculator loop.

Hi, I am trying to make a maths calculator that: 1. Prompts the user for a number. 2. Prompts the user for an operation (add, subtract, divide or multiply) 3. Prompts the user for a number. 4. Prompts the user for another operation (same as above) OR the option to get the result for the... (4 Replies)
Discussion started by: johnthebaptist
4 Replies

7. Shell Programming and Scripting

Using IF statements with maths where the input is not an integer

Hi All I've made a few scripts which using GDAL extract the value of a pixel within a given raster. The purpose is to work out the combine value of every pixel. I thought there may have been an easier way to do this but alas! The code below extracts the pixel value at position X Y. The... (3 Replies)
Discussion started by: StudentFitz
3 Replies

8. Shell Programming and Scripting

Perl - maths equation - need help

if input to the perl program is ' ( p * ((a+b) * (c+d))) + q ' it shuld give the output as ' pac + pad + pbc + pbd + q ' .can anyone suggest a way to do this ? (7 Replies)
Discussion started by: Anuj8584
7 Replies

9. Programming

How to convert byteArray variables to HexaString variables for Linux?

Hello everybody, I am having problem in converting byte array variables to Hexa String variables for Linux. I have done, converting byte array variables to Hexa String variables for Windows but same function doesn't work for linux. Is there any difference in OS ? The code for Windows is given... (2 Replies)
Discussion started by: ritesh_163
2 Replies

10. Shell Programming and Scripting

Problem with Maths

Heres a script i wrote as a bit of practise. What it does is insert a line in the middle of a file. The line being $1 and the file being $2 #!/bin/bash rm tempfile touch tempfile count=1 linenum= `wc -l < $2` if then echo $1 >> $2 else even=`expr "$linenum" % 2` if then... (3 Replies)
Discussion started by: Quesa
3 Replies

Featured Tech Videos