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[RS]

On 24/03/18 09:43, Ralph Corderoy wrote:

>>>>> If you are typing `get_player .* --since 70' into a Linux shell
>>

> 
> The shell is expanding globs before invoking get_iplayer, thus they're
> not seen by get_iplayer if they match anything.  If they don't match
> anything then they normally remain and are passed to get_iplayer anyway.
> For the arguments get_iplayer does see, it decides to interpret some of
> them as regexps.
> 
> «get_iplayer Railway» has no glob metacharacters to expand so one
> argument is passed to get_iplayer, it uses it as a regexp, it has no
> regexp metacharacters so effectively is a substring search of the
> titles.
> 
> «get_iplayer R.*way» has a glob metacharacter, the «*», the shell looks
> at the current directory for entries starting «R.» and ending «way».
> There are none.  The glob remains, unexpanded.  get_iplayer has one
> argument, «R.*way» that it uses as a regexp.  There's two regexp
> metacharacters, «.*», meaning zero or more of any character, used in the
> search.
> 
> «get_iplayer R.*way» is run again, and again has a glob, the «*».  This
> time, the current directory has «R.steinway» in it.  The argument with
> the glob is expanded into that and get_iplayer has one argument,
> «R.steinway», that's used as a regexp.  It's unlikely to match any
> titles, e.g. «Resteinway».
> 
> To avoid glob expansion, quote the glob metacharacters, «get_iplayer
> 'R.*way'», and get_iplayer sees the regexp «R.*way».
> 
>> One thing that does not appear to have happened is infinite recursion,
>> or even matching of additional programmes.
> 
> Your unquoted «.*» on Linux would often expand to «. ..», and perhaps
> more if you've other `dot' files present.  These are two regexps
> interpreted by get_iplayer.  It prints titles matching either.  Since
> anything matching the second is also matched by the first, you are
> seeing any title at least one character long.  That's almost like «.*»
> and «^» except that a zero-length title won't be matched.
> 
Hi Ralph

I can see that in some special cases leaving out the quotes will give 
wrong results.  I only wanted a crude indication of how long it had been 
since refreshing the cache had been working, but that is no excuse for 
getting it wrong.

I clearly still need to think it through further.  I would have expected
get_iplayer * --since 110
to match 67 programmes, but it matches 0.

I would have expected
get_iplayer '*' --since 110
to match 0 programmes but it matches 67.

If I put in an invalid regex

get_iplayer *. --since 110
get_iplayer '*.' --since 110

both seem to reach Perl as a regex even though the first has a bash 
wildcard.

Quantifier follows nothing in regex; marked by <-- HERE in m/* <-- HERE 
./ at /usr/bin/get_iplayer line 1245.

Best wishes
Richard