Question

While searching for a unix problem, I came across the following string splitting regular expression statement:

 string="[e-mail];[e-mail];[e-mail]"
    str1=${string%%;*} 
    str2=${string##*;}

    Result:
    str1=[e-mail] 
    str2=[e-mail]

I did not understand the second expression(str2).
Can please someone help.

Thanks

Answer 1

From the bash manual, under Parameter Expansion:

   ${parameter#word}
   ${parameter##word}
          The word is expanded to produce a pattern just as in pathname expansion.  If the pattern matches  the  beginning  of  the
          value  of  parameter, then the result of the expansion is the expanded value of parameter with the shortest matching pat-
          tern (the ``#'' case) or the longest matching pattern (the ``##'' case) deleted.  If parameter is @  or  *,  the  pattern
          removal 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 pattern removal operation is applied to each member  of  the  array  in
          turn, and the expansion is the resultant list.

   ${parameter%word}
   ${parameter%%word}
          The  word  is  expanded to produce a pattern just as in pathname expansion.  If the pattern matches a trailing portion of
          the expanded value of parameter, then the result of the expansion is the expanded value of parameter  with  the  shortest
          matching pattern (the ``%'' case) or the longest matching pattern (the ``%%'' case) deleted.  If parameter is @ or *, the
          pattern removal 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 pattern removal operation is applied to each member of the
          array in turn, and the expansion is the resultant list.