helpThe GNU Bourne-Again SHell - Support: sr #109348, [Syntax extension] Nested...


sr #109348: [Syntax extension] Nested transformations within variable expansions

Submitted by:  None
Submitted on:  Sun 09 Jul 2017 05:56:12 PM UTC  
Category:  None Priority:  5 - Normal
Severity:  2 - Minor Status:  None
Privacy:  Public Assigned to:  None
Originator Email:  -email is unavailable- Open/Closed:  Open
Operating System:  None

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Sun 09 Jul 2017 05:56:12 PM UTC, original submission:

Motivation :

The current variable expansion syntax allows one to perform very useful substitutions (such as removing a prefix or suffix, or replacing one) on a one-off basis. However, it only allows a single such substitution to be performed at a time. If I have a variable in which I need to replace both a prefix and a suffix, I have no choice but to use an intermediate variable :

srcs=( src/*.c )
x=( "${srcs[@]/#$SRC/$OBJ}" )
command ... "${x[@]/%.c/.o}"

I would propose that the previous example be expressible as follows, in a single expansion :

srcs=( src/*.c )
command ... "${{srcs[@]/#$SRC/$OBJ}/%.c/.o}"

The substitutions would take place in a left-to-right (or innermost-to-outermost) order, on every element of the leftmost array or variable name, just like they do now.

As far as I know, the nested braces don't clash with any existing variable-name syntax, and since they are already a delimiting element of parameter patterns, they arent likely to clash with pattern syntaxes either.

Thank you for your attention, and keep up the good work



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