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Re: help with pattern matching needed
From: |
Chet Ramey |
Subject: |
Re: help with pattern matching needed |
Date: |
Fri, 7 Jan 2022 12:05:27 -0500 |
User-agent: |
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.4.1 |
On 1/7/22 2:20 AM, Lawrence Velázquez wrote:
Case 2:
*******
A string like:
[.*^$[\]
should end up (after quote removal) as the pattern:
[.*^$[]
an AFAIU be valid (but of course not match the literal \), but bash
complains about a missing matching ].
That construct executes e.g. in (d)ash, though it never matches (or at
least not with the plain single characters).
It looks like \] is being treated as a literal ] in both cases.
The difference seems to be in the parsing: dash gives up on the
bracket expression, while bash consumes the rest of the script
trying to close it.
% cat ex1.sh
case $1 in
[.*^$[\]) printf '%s matched\n' "$1" ;;
*) printf "%s didn't match\\n" "$1" ;;
esac
The parser sees the (deprecated) `$[' and tries to read an entire `$[]'
expansion as part of a word. It fails to close that expansion and reports
an EOF error.
That is it, though. The empty $[] substitutes "0" into the pattern.
% cat ex2.sh
case $1 in
[.*^$[]) printf '%s matched\n' "$1" ;;
*) printf "%s didn't match\\n" "$1" ;;
esac
% bash ex2.sh '[.xxxxxxx^0'
[.xxxxxxx^0 matched
However, as you noted, bash doesn't parse quite so greedily this
time. I don't know why not.
Because the closing `]' isn't escaped and the $[] expansion is complete.
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU chet@case.edu http://tiswww.cwru.edu/~chet/
- help with pattern matching needed, Christoph Anton Mitterer, 2022/01/07
- Re: help with pattern matching needed, Christoph Anton Mitterer, 2022/01/07
- Re: help with pattern matching needed, Chet Ramey, 2022/01/08
- Re: help with pattern matching needed, Christoph Anton Mitterer, 2022/01/10
- Re: help with pattern matching needed, Christoph Anton Mitterer, 2022/01/11