> -----Original Message----- > From: Stephane Chazelas <stephane.chaze...@gmail.com> > Sent: Thursday, May 30, 2019 10:14 PM > To: Steven Penny <svnp...@gmail.com> > Cc: austin-group-l@opengroup.org > Subject: Re: Arrays
> > In there, instead, a list was stored in a *scalar* variable and split (and > globbed) upon expansion when unquoted as in: > > files='file1 file2' > rm -f -- $files # with IFS assumed to contain its default value > > Instead of > > files=(file1 'file 2') > rm -f -- $files > > (or equivalent) in csh, rc, es, fish... > > That was a very bad design probably explained by a desire of Steve Bourne to > maintain some level of backward portability with the > Thompson shell parameter expansion (where it was more like macro expansion). > That misfeature is by far the primary source of bugs and > shell script security vulnerabilities nowadays (see > https://unix.stackexchange.com/questions/171346/security-implications-of-forgetting-to-quote-a-variable-in-bash-posix-shells) I think the macro expansion idea came from Louis Pouzin/Multics, as described in https://multicians.org/shell.html: Then in 64 came the Multics design time, in which I was not much involved, because I had made it clear I wanted to return to France in mid 65. However, this idea of using commands somehow like a programming language was still in the back of my mind. Christopher Strachey, a British scientist, had visited MIT about that time, and his macro-generator design appeared to me a very solid base for a command language, in particular the techniques for quoting and passing arguments. Without being invited on the subject, I wrote a paper explaining how the Multics command language could be designed with this objective. And I coined the word "shell" to name it. It must have been at the end of 64 or beginning of 65. The macro generator in question is GPM, General Purpose Macrogenerator. Regards Konrad
