bash substring manipulation problem

fitteschleiker · 04-07-2010, 08:52 AM

Hi my script has a variable which comes in the form +00.00 +0.00 -00.00 or -0.00 (the numbers can be any in that form)

for any that have a + symbol I need to remove the +, but if it has a - symbol it needs to stay. i need to make a new variable with the string from the old variable btut without any plus sign.

I have tried a lot of different ways with no success, each thing I tried either left the + or removed the entire string.

I think this should work but doesn't

foo=+12.40
bar=${foo#+}

any ideas anyone?

catkin · 04-07-2010, 08:59 AM

Code:

c@CW8:~$ foo=+12.40
c@CW8:~$ echo ${foo//+/}
12.40

EDIT:

Code:

c@CW8:~$ foo='+00.00 +0.00 -00.00 or -0.00'
c@CW8:~$ echo ${foo//+/}
00.00 0.00 -00.00 or -0.00

fitteschleiker · 04-07-2010, 09:12 AM

OMG thankyou

I have been searching everywhere!

and thats not in my book...

in fact looking at the man page, I still don't quite understand what you did..

I'm guessing ${parameter/pattern/string}
Pattern substitution.

well thanks again, been pulling my hair out, now i can finish this bugger

grail · 04-07-2010, 09:38 AM

You can check it out here:

http://tldp.org/LDP/abs/html/string-manipulation.html

catkin · 04-07-2010, 12:13 PM

Quote:

Originally Posted by fitteschleiker

I'm guessing ${parameter/pattern/string}
Pattern substitution.

Glad it is solved for you

The // means global (all instances) replace. Reference info here (scroll down to last expansion). Personally I find the GNU Bash Reference easier to use (table of contents and all on one page) than the Advanced Bash Scripting Guide (as per grail's post) but the ABS has examples which can be helpful. Actually the GNU Bash Reference is very close to the man page:

Code:

       ${parameter/pattern/string}
       ${parameter//pattern/string}
              The pattern is expanded to produce a pattern just as in pathname expansion.  Parameter is expanded and the  longest  match  of
              pattern  against  its  value  is  replaced with string.  In the first form, only the first match is replaced.  The second form
              causes all matches of pattern to be replaced with string.  If pattern begins with #, it must match at  the  beginning  of  the
              expanded  value  of  parameter.   If  pattern  begins with %, it must match at the end of the expanded value of parameter.  If
              string is null, matches of pattern are deleted and the / following pattern may be omitted.  If parameter is @ or *,  the  sub‐
              stitution operation is applied to each positional parameter in turn, and the expansion is the resultant list.  If parameter is
              an array variable subscripted with @ or *, the substitution operation is applied to each member of the array in turn, and  the
              expansion is the resultant list.