REAL-WORLD CHALLENGES
Whitespace cleanup
Practical substitutions: collapse space runs and strip trailing whitespace.
Replace every run of two or more spaces with a single space. The pattern matches the run, the replacement is one space. ` {2,}` reads as "a space, two or more times" - so "a b" (three spaces) becomes "a b".
Why two or more, not one or more? Replacing every single space with a space works too, but it touches text that is already fine. Precise patterns make precise edits - it matters once you run substitutions over real files.
PRACTICE - 2 DRILLS 0/2 DONE
Collapse every run of multiple spaces into one space.
s/
->
too many spaces
must become:
too many spaces
already clean
must become:
already clean
a b c
must become:
a b c
Remove trailing spaces and tabs at the end of every line. Replace them with nothing.
s/
->
line one line two clean
must become:
line one line two clean
alpha beta
must become:
alpha beta
nothing to trim
must become:
nothing to trim