Surprisingly, string matching is faster than substring-ing.
# s is ':' repeated (6 * 2^i) times
s=$(s=::::::; i=12; while [ $i -gt 0 ]; do i=$((i-1)); s="$s$s"; done; echo
"$s") \
hyperfine -w2 -S bbox-master/sh 'while [ "$s" ]; do s=${s#????}; done' 'while
[ "$s" ]; do s=${s:4}; done'
Summary
'while [ "$s" ]; do s=${s#????}; done' ran
1.16 ± 0.00 times faster than 'while [ "$s" ]; do s=${s:4}; done'
The slowdown doesn't depend much on the skip parameter -- ${s:1} as well as
${s:16} are slower than corresponding pattern matches. There are jump points if
$s gets much longer or much shorter.
I'm curious -- the SUBSTR code seems to check for quotes and CTLESC in vstr, so
I guess... it can substring in unprocessed (shell) strings? When does this come
into play -- it's not like one can write ${"a\\bc":2}?
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