Help with calculator code

Shell Programming and Scripting
1

Hi Guys,

I found this code in net.. it is working fine..
But can anybody explain me the sed statement used in the code..

    echo "Enter the expression:\c"
read express
eval echo "$express"|sed 's/^/'$precision' \
/'|bc -l|\
    sed -n '1,${
        /syntax/!{
        }
        /syntax/{
            a\
                Possible causes:\
                1. Error in expression\
                2. Variable not enclosed in (), supplied -ve value\
                3. Exponents given as non-integers
        }
        s/\([ ]*\)\([^ ]*\)/\2/p
    }'

Thanks For your help in advance..

Regards,
Magesh

---------- Post updated 02-02-10 at 12:40 AM ---------- Previous update was 02-01-10 at 08:35 PM ----------

Guys come on man.. i was counting on you people

2

Hi,

I'm learning sed with:
Sed - An Introduction and Tutorial

So:

Ask for expresion:

echo "Enter the expression:\c"
read express

Appended some precision variable (must have been definited before) and run through bc (calculator)

eval echo "$express"|sed 's/^/'$precision' \
/'|bc -l|\

Don't print anything if not request by /p argument (-n switch) on every line (1,$).

    sed -n '1,${

If no "syntax" in line was found - don't print nothing.

        /syntax/!{
        }

For lines that do contain "syntax" word:

        /syntax/{

... append more explanation:

            a\
                Possible causes:\
                1. Error in expression\
                2. Variable not enclosed in (), supplied -ve value\
                3. Exponents given as non-integers
        }

Finally, print the word first word (string/digits) of lines which are starting with whitespaces. I guess this is a format of bc final result.

 
        s/\([ ]*\)\([^ ]*\)/\2/p
    }'

Not bad for an hour of reading, I guess. Please correct me if I'm wrong - I'm just learning.

3

Thanks man.. really appreciated.