#7 [p]bosh: Parameter substitution: unable to trim arbitrary prefix/suffix

[Avi Halachmi]

The following is reproducible with bosh and pbosh (tested schily-tools 2018-09-26, but I think it also happens with earlier versions).

I believe the following invocation should print the last char of $1 for any arbitrary $1:

posh -c 'in=$1; pre=${1%?}; out=${in#"$pre"}; printf [%s] "$out"' -- AB\"C

Expected result: [C]
Actual result: ["C]

For plain strings like ABC it does work.

I tried all 4 combinations of outer quotes ( out="${...}" ) and inner quotes ( out=${ .. "$pre" .. } ) and none worked. I believe at the very least either inner-only or inner+outer quotes should always work for arbitrary $1.

Tested on Ubuntu 18.04 LTS x64 with gcc 7.3.0, gnu make 4.1 .

All other shells which I tested perform as expected on any arbitrary $1 which I tried (including complex strings with single/double quotes, backslashe, shell reserved words, etc). I tested ksh93/dash/bash/mksh/yash/busybox-ash , and additionally also in posix-compliant mode with bash/yash/mksh.

[Avi Halachmi]

Oops typo.. in posh -c I meant bosh or pbosh.

[Jörg Schilling]

Please check the attached patch.

The problem here: It passes my unit test suite, but this may not be sufficient. So if you have more tests, please run them....

[Avi Halachmi]

Confirmed that the patch fixes the test case and [p]bosh now print [C]. Thanks.

I'll let you know if I find other issues.

FWIW, I wrote and use this tool to compare output from different shells (the tool itself runs fine in [p]bosh), mostly to make sure constructs I use in scripts are as compatible as possible:
https://github.com/avih/shcmp

[Jörg Schilling]

The new version is available for download