Adding Signed numbers

[ojosVerdes]

How do you add signed number. for example when I do this I get an error;

expr +5 + +5 or expr 5 + +5

but I don't get an error when I do this:
expr -5 - -5

why?

Thanks

 

[olded]

Hi:

I tried adding signed numbers with expr under Solaris 7 ksh and Linux 7.3 bash, and if fails - just as it failed for you. Why? must be a limitation of expr. It's probably that way on most any unix flavor.

However, if you use the ksh arithmetic expressions to add numbers, it works:

#!/bin/ksh

x=$((+10 + 5))
echo $x

Go figure.

Ed

 

[ojosVerdes]

How would you do if you are not using korn Shell?

I want to be able to add signed numbers. how do I remove the + sing off the mumber so I don't get an error number?

Thanks

Frank

 

[jamisar]

prepend '-1+1' to the '+' sign
use the faster 'bc'
echo "-1+1+5 -1+1+ -1+1+5"|bc -----------
when they don't ask you anymore, where they are come from, and they don't tell you anymore, where they go ... you'r getting older !

 

[ojosVerdes]

Thanks Jamisar,

Question for you.
How do I translate this to unix?
If first character of a variable is equal to + then cut the first character, and store the the result into a varible.

ex:

echo +6 |cut -c2
yields 6

how do I check to see if the first character in a variable is a + sign?

Thanks

 

[jamisar]

echo $string|sed -e 's/+//g' -----------
when they don't ask you anymore, where they are come from, and they don't tell you anymore, where they go ... you'r getting older !

 

[vgersh99]

#!/bin/ksh

a="+6"
#a="6293874"
#a="abcd"

if [[ $(expr "${a}" : '^[+][0-9]') -ne 0 ]] ; then
echo "[${a}] signed"
else
echo "[${a}] NOT signed"
fi;
vlad
+---------------------------+
|#include<disclaimer.h> |
+---------------------------+

 

[ojosVerdes]

vlad,
Is there any reason why this does not work in Borne Shell?

Frank

 

[vgersh99]

for Bourne, use:

if [[ `expr &quot;${a}&quot; : '^[+][0-9]'` -ne 0 ]] ; then vlad
+---------------------------+
|#include<disclaimer.h> |
+---------------------------+

 

[ojosVerdes]

Thanks vlad. U R a genius.

Do U know any good book that can teach me about regular expresions?

 

[vgersh99]

you can start with these links - you'll find more as you 'drill down'.

http://dmoz.org/Bookmarks/E/era/For...gory,_when_I_can_figure_out_where_it_belongs/

http://sitescooper.org/tao_regexps.html

http://etext.lib.virginia.edu/helpsheets/regex.html

http://www.opengroup.org/onlinepubs/7908799/xbd/re.html

all the best.

vlad
+---------------------------+
|#include<disclaimer.h> |
+---------------------------+