On 9/4/22 10:48 PM, Hyunho Cho wrote:
Bash Version: 5.1
Patch Level: 16
Release Status: release
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#### "gcc --help" is already a short string, but the system hangs.
A short string? It's 90K on my system.
( without using extended pattern, there is no such problem )
bash$ help=$( gcc --help )
bash$ echo "${help//+([$' \t\n'])/ }"
So what you're doing is taking a 90K string, and for each character in the
string, trying to match it against successively shorter substrings,
starting at the end to preserve the required `leftmost longest' match
semantics. It's worse because you can't calculate the pattern length here,
so you can't bound the search at all. Nor are you building a regular
expression and trying to execute it against the strings; this is just a
simple pattern matcher.
It's hard to think of a less efficient way of doing whatever it is you're
trying to do.
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU [email protected] http://tiswww.cwru.edu/~chet/
