Passing asterisk As A Parameter

Thread Tools Search this Thread
Top Forums Shell Programming and Scripting Passing asterisk As A Parameter
# 1  
Old 07-11-2008
Error Passing asterisk As A Parameter

I have written a Shell Script Program which accepts 3 parameters as shown below:

./calc 20 + 2

in the above line ./calc is the Shell Script itself with 3 parameters, namely:

and 2.

Well, now let's look inside the Script:

echo $result

The output will be as per our expectation:


But well, let's change the sign in the 2nd parameter being passed:

./calc 20 - 2

./calc 20 / 2

All those there examples have no issues so far!

But when we pass * as a parameter
./calc 20 * 2

things go bad!

Instead of *, the result of "ls *" command or simply the directory list gets passed to the variable: $2.

So, how can I make this Calculator program a user friendly one? I have been suggested to use '*' (I have not tried it yet, however) but it doesn't seem to be a User Friendly Way of writing any script or program, does it?


# 2  
Old 07-11-2008
Escape the asterisk
./calc 20 \* 2

# 3  
Old 07-11-2008
./calc bill \* gates

and you'll get a ls listing again. Escaping the asterisk only seems to work on numerals. Does anyone know a workaround?
# 4  
Old 07-11-2008
If you have the bc package installed, this script works:
echo "$@" | bc

But you do have to quote the asterisk as suggested: calc 20 \* 2

BTW, try using your script in a directory that has no files. That is, try this:

mkdir empty
cd empty
../calc 20 * 2
cd ..
rmdir empty
# 5  
Old 07-11-2008
Originally Posted by na5m
./calc bill \* gates

and you'll get a ls listing again. Escaping the asterisk only seems to work on numerals. Does anyone know a workaround?
If typing an extra command before & after you're done using the 'calc' utility is acceptable, you could type "set -f" first... ("set +f" to set it back when you're done)...
(Unfortunately, putting this command inside your script won't work, since by the time the script is executed, the * special character will already be expanded...)
# 6  
Old 07-18-2008
Well, I tried this code segment:

./calc 10 '*' 5

and also this one

./calc 10 "*" 5

and both of them worked. But it is not user-friendly, is it?
# 7  
Old 07-18-2008
One thing you might try is using the double parens math workings of bash. Quite cool and is readable, and it avoids your shell expansion problem. Secondarily, a "here" document with the "dc" program is how I used to do it. e.g.:

dc <<EOF
2 20 * p
will produce 40 as output

Using the double-parens syntax of bash, one can do this:

echo $i <-- produces 40

Kinda cool, huh?

Last edited by fsahog; 07-18-2008 at 11:47 PM.. Reason: To illustrate more fully
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Passing parameter through file

Hi , I am passing date parameter through file my shell script is #set -x #set -v asd=$1 asd1=$2 echo $asd echo $asd1 Passing parameter as below sh `cat file1.txt` Output (2 Replies)
Discussion started by: kaushik02018
2 Replies

2. Shell Programming and Scripting

Passing parameter more than 9

Hi, I've written a script where eleven parameter to be passed from command line which is inserting into an oracle table, it is working but the tenth and 11th parameter are not accepting as given it is referring to 1st parameter. HERE IS THE SCRIPT #!/bin/ksh #set -o echo $*... (4 Replies)
Discussion started by: sankar
4 Replies

3. Shell Programming and Scripting

Passing parameter to script, and split the parameter

i am passing input parameter 'one_two' to the script , the script output should display the result as below one_1two one_2two one_3two if then echo " Usage : <$0> <DATABASE> " exit 0 else for DB in 1 2 3 do DBname=`$DATABASE | awk -F "_" '{print $1_${DB}_$2}` done fi (5 Replies)
Discussion started by: only4satish
5 Replies

4. Programming

passing float parameter

I am surprised by GCC (this is ver. 4.2.4, Ubuntu 32 bit Intel) when a function declares a float parameter and it's prototype is missing, the parameters are messed up. Please see my code below: ~/test$ cat x1.c #include <stdio.h> #include <stdlib.h> set_p(int p1, float p2, int p3, int p4)... (7 Replies)
Discussion started by: migurus
7 Replies

5. Shell Programming and Scripting

Positional parameter passing

Hi All, When passing parameters to a sheel script, the parameters are referenced by their positions such as $1 for first parameter, $2 for second parameter. these positional values can only have values ranging from $0-$9 (0,1,2,3...9). I have a shell script meant to accept 20 parameters. for... (3 Replies)
Discussion started by: ogologoma
3 Replies

6. Shell Programming and Scripting

Passing parameter in quotes

Hi, PW='/as sysdba'; export PW in other module I call sqlplus ${PW} (this line I unable to change!) How I can define PW so that sqlplus calls PW in quotes i.e sqlplus '/as sysdba' I tried like this PW="'/as sysdba'"; export PW - no luck Thanks in advance (2 Replies)
Discussion started by: zam
2 Replies

7. Shell Programming and Scripting

passing asterisk to a script as variable

I'm writing a script that will ssh to a number of hosts and run commands. I'm a bit stumped at the moment as some of the commands that I need to run contain wildcards (i.e. *), and so far I have not figured out how to escape the * character so the script doesn't expand it. More specifically, here's... (9 Replies)
Discussion started by: GKnight
9 Replies

8. Programming

Passing parameter to makefile?

Hi, How to pass parameter to makefile? Please let me know if any one knows and also please put an example of makefile with this feature. thanks, Manju. (3 Replies)
Discussion started by: manju_p
3 Replies

9. UNIX for Advanced & Expert Users

Parameter passing in a function

I need to pass a parameter to a function in a script. My parameter is a string. When I display the parameter within my function, I only get the first word from string I pass in. How can I make the function receive the whole string (and not terminate at the first space it encounters)?. part of... (2 Replies)
Discussion started by: fastgoon
2 Replies

10. Shell Programming and Scripting

parameter passing

Hallo everyone, This is my problem below: /home/cerebrus/pax=>vat ksh: vat: not found /home/cerebrus/pax=>cat #!/bin/ksh set -x bdf|grep appsdev|awk '{ print $5 }'> class3 dd={cat class3} echo $dd /home/cerebrus/pax=> /home/cerebrus/pax=>./ + bdf +... (8 Replies)
Discussion started by: kekanap
8 Replies
Login or Register to Ask a Question

Featured Tech Videos