Re: Cookbook example (fwd)

[Sudarshan Raghavan]

Not sure if this mail was sent properly, my apologies if you already have 
recd this.

On Tue, 3 Sep 2002, ANIDIL RAJENDRAN wrote:

> Newbie again.
> Sorry if this question sounds so silly
> 
> Want to open filenames like ~username/blah but open doesn't interpret the tilde to 
>mean the
> home directory
> 
> Solution 
> 
> expand the filename manually with substitution
> 
> $filename =~ s{ ^  ~  ( [^/]* ) }
>   { $1
>? (getpwnam($1)) [7]
>: ( $ENV{HOME} || $ENV{LOGDIR}
>   || (getpwuid($>)) [7]
>  )
> }ex;
> 
> The auther says the following can me matched
> ~user
> ~user/blah
> ~
> ~/blah
> 
> Could someone make me clear how these can be matched by the pattern inside the 
>parenthesis 
> which is ( [^/]*)
> 

First up the two modifiers 'e' and 'x' used at the end. (perldoc perlre)
The e modifier specifies that the replacement part of the substitution is
to evaluated as perl statements and the result used for the substitution.

The x modifier tells the regex engine to ignore whitespaces and the '#'
character. This allows you to write a readable pattern match with
comments.

The search part of the substitution
{ ^  ~  ( [^/]* ) }

Note with /x modifier on, the white spaces will be ignored.
This says look for '~' at the start of $filename followed 0 or more non 
'/' characters which will be saved in $1.

The replacement part
{ $1
? (getpwnam($1)) [7]
: ( $ENV{HOME} || $ENV{LOGDIR}
   || (getpwuid($>)) [7]
  )
}ex;

Read through these docs, (perldoc -f getpwnam) and (perldoc -f getpwuid).
This uses the ternary operator, if $1 is true the statements after '? and 
before ':' will be evaluated. If it is false that after ':' will be 
evaluated. (perldoc perlop)

When $filename is '~' $1 contains nothing i.e. evaluates to false.
This means '~' is substituted by the result of the statements after ':'.

When $filename is '~user' $1 contains 'user', this means '~user' is 
substituted by the results of (getpwnam($1))[7].








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Re: Cookbook example (fwd)

[Felix Geerinckx]

on Thu, 05 Sep 2002 10:02:03 GMT, [EMAIL PROTECTED] (Sudarshan
Raghavan) wrote: 

> Not sure if this mail was sent properly, my apologies if you
> already have recd this.

It was, as you could have found out yourself by going to

  

(or by using a newsreader instead of an email program ;-)

-- 
felix

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