Trig functions in the Korn Shell?

[Simon Ingram]

Hi folks,

I have read that the Korn Shell has built in Trig functions like sine and cosine. Imagine my disappointment when I get an unknown function message.
I am running on a MAC with OS X. It has a Korn shell, but I don't know if its ksh 88 or ksh 93. There should be a way of interrogating the system for this info, but I don’t know how.
I tried uname –a but it didn’t help. I would be very surprised if I am using the old Korn which raises the question: why don’t the trig functions work?

Here’s my test script:

#!/bin/ksh
##
val=$( bc -l <<EOF
a(1) # arctan 1 is 45 degrees
EOF)
##
echo $val
#
## shell trig functions
sin45=$(( sin($val) ))
echo $sin45

When I run it:

$ ksh simon_bc
.78539816339744830961
simon_bc[10]: sin(.78539816339744830961) : unknown function

AM I missing something?

With thanks and Best Regards
Simon>

[Ulf Dittmer]

I don't think the version of the shell (Korn or otherwise) has anything to do with that - you're invoking the "bc" executable that is part of all Unix-like OSs: http://pubs.opengroup.org/onlinepubs/9699919799/utilities/bc.html.

The sine function is called "s", not "sin".

[Simon Ingram]

Hi Ulf,

thanks for the reply. You are partially correct, if I had tried to execute the sine function within bc then it would be "s" not "sin". But in the script the bracket after EOF (line 5) terminates the bc command and everything following is executed in the shell. The sine command in the korn shell is "sin" not "s".

In fact we can ignore the bc altogether and just try to execute the sin command in the shell hardcoding the argument. I can't get it to work! Arithmetic syntax error.

Best Regards

[Ulf Dittmer]

No idea about the shell. Why don't you use bc for the entire calculation? It would seem to be better suited than any shell.

[Simon Ingram]

You are right, there are many ways to get the job done, but I am interested in the Korn shell and what it can do. I have a book on the shell, that tells me it can do trig functions and when I put in an example from the book, I get an error. It's kind of exasperating! I just wonder what I'm doing wrong.

[Ulf Dittmer]

A quick googling shows that those functions apparently need to be in double parentheses, but not a $ sign: https://suite.io/mark-alexander-bain/zfj2aa
This works fine on OS X:

$ (( d = sin(1.0) ))
$ echo $d
0.841470984807896507

[Simon Ingram]

Hi Ulf,

many thanks for your persistence. Here is my program: trig_test.ksh

#!/bin/ksh
(( d = sin(1.0) ))
echo $d

/Users/simoningram/unix/bin => trig_test.ksh
/Users/simoningram/unix/bin/trig_test.ksh: line 3: d = sin(1.0) : arithmetic syntax error

I too have used google and tried all the different syntax variations, but this problem is more fundamental, as I suggested in my first post.

Best Regards
Simon

[Ulf Dittmer]

Hm, strange. I actually stand corrected in that within a script, the $ is needed. But is still works fine for me on Mavericks:

[~] ulf% more trig_test.ksh 
#!/bin/ksh
##
val=$( bc -l <<EOF
a(1) # arctan 1 is 45 degrees
EOF)
##
echo $val
#
## shell trig functions
sin45=$(( sin($val) ))
echo $sin45 

[~] ulf% ./trig_test.ksh
.78539816339744830961
0.707106781186547524
[~] ulf% 

[Simon Ingram]

Hi Ulf,

I haven't installed Mavericks. Maybe I should do that?

[Ulf Dittmer]

I have never used the Korn shell before, so I don't know what difference the OS X version
makes.

[Simon Ingram]

Mavericks didn't make any difference.
The strange thing is that I ran this script on my Mac at home and on our unix system at work and in both cases it fails. I will investigate this at work with our specialists, but it is very good to know that you have managed to get the script working on your system, so thanks Ulf.

[Andrew Monkhouse]

Works fine for me as well, using Mountain Lion and ksh version 93u 2011-02-08