Question

Assuming a variable contains spaces, newlines, and tabs followed by some text, why does this:

${var#'${var%%[![:space:]]*}'}  # strip var of everything                                  # but whitespace                                 # then remove what's left                                  # (i.e. the whitespace) from var 

remove the white space and leave the text, but this:

${var##[:space:]*}  # strip all whitespace from var 

does not?

Answer 1

If I set var=' This is a test ', both your suggestions do not work; just the leading stuff is removed. Why not use the replace functionality that removes all occurrences of whitespace and not just the first:

 ${var//[[:space:]]}