我在 release notes of Bash 5.1 中读到:
p. BASH_REMATCH is no longer readonly.
如 Bash Reference Manual 中所述:
The array variable BASH_REMATCH records which parts of the string matched the pattern. The element of BASH_REMATCH with index 0 contains the portion of the string matching the entire regular expression. Substrings matched by parenthesized subexpressions within the regular expression are saved in the remaining BASH_REMATCH indices. The element of BASH_REMATCH with index n is the portion of the string matching the nth parenthesized subexpression.
是的，访问正则表达式的匹配项非常有用:
$ DESERT=pie-cake_berry_cream-sirup
$ [[ $DESERT =~ _(.*)_ ]] && echo "${BASH_REMATCH[1]}"
berry
但是，我看不出这个消息在 Bash 5.1 中有什么用。也就是说，BASH_REMATCH 不是只读的有什么意义？
最佳答案
在this bug-bash mailing list thread ，bashdb 的维护者(一个 Bash 调试器)解释说 BASH_REMATCH 的值可能会在调试钩子(Hook)内部发生变化，并且由于该变量是只读的，因此可以通过运行最初再次设置它的命令来重置它，这很棘手又脆弱:
Current in bash 5.0 and earlier, the value of BASH_REMATCH might chanted inside a debug hook.
Since BASH_REMATCH is read-only, resetting the value on hook return to the debugged program is a bit tricky and fragile...
[...]
The way that bashdb currently resets BASH_REMATCH is to reissue the command that caused the value to get initially set. That is fragile since this set on exit between stepping from the time BASH_REMATCH was set until the time it is last used. In between variables used in the regular expression may have changed.
[...]
Restoring it is just as tricky. As I hope you see all of this is a bit fragile.
在response , Chet 提出让它不是只读的:
How about we just make it not read-only? The shell will still set it when it does regexp matching.
关于bash - BASH_REMATCH 在 Bash 5.1 中不是只读的有什么用？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/65669036/