Help: removing a variable substring from a string variable in sh script

gnparsons · 06-04-2008, 12:18 PM

Hi All,
I'm a programmer, but a *nix noobie. Im writing a script that needs to do the following:

=========================
Precondition:

List_String=item1,item2,item3,...itemN
Item_to_be_removed=item2

Magic Happens Here

Postcondition:

List_String=item1,item3,...itemN
Item_to_be_removed=item2

#note: Item_to_be_removed may be item 1 ... itemN, which should be removed the same as this example's item2.
#note2: Item_to_be_removed may be something not even in the list_string, in which case it should fail silently (because that is actually the case we are hoping for)

======================
I'm just not sure what the Magic function is/how to format it
List_String=`echo List_String | sed 's/$Item_to_be_removed//g'` ?
List_String=${$List_String//Item_to_be_removed/} ?

I could just write a compiled program that would do this one function, but I'm certain that there is a better/more elagent way already built in that I can call from the shell script.

Currently looking into awk script.

Thanks in advance,
-Greg

bigearsbilly · 06-04-2008, 04:41 PM

List_String=`echo List_String | sed 's/$Item_to_be_removed//g'` ?

lose the backquotes

Code:

$ 
x=item2                                 
$ echo item1,item2,item3,...itemN| sed "s/$x//g"
item1,,item3,...itemN

gnparsons · 06-04-2008, 05:21 PM

Thanks!

For posterity, the final version of the magic code looked somethign like this:

Code:

List_String=`echo List_String | sed "s/$Item_to_be_removed[,?]//g"`
List_String=`echo List_String | sed "s/[,?]$Item_to_be_removed//g"`

I'm sure that it could be improved (my regex-foo is very weak) but it was sufficient to resolve the issue.

Thanks again,
-Greg