The or thing.

nasa has asked for the wisdom of the Perl Monks concerning the following question:

I eneter a script and want to go one way if either one of two files exist
or anouther way if neither of the two files exist. To the best of my knowledge || means or. So I make .

if (-e "data/$file.data") || (-e "data/$otherfile.data") 
{
    print " <BR>Hooray at least one of the the files exists";    
}

else {
    print "<BR>Hohum neither of the files exist";
}
[download]

So I tried

if (-e "data/$file.data") or (-e "data/$otherfile.data") 
{
    print " <BR>Hooray one of the files exist";    
}

else {
    print "<BR>Hohum neither of the files exist";
}
[download]

I cant find any information on this in the limited tutorials I have.
Can somone please show me the simple solution.

Comment on The or thing. Select or Download Code

Replies are listed 'Best First'.
Re: The or thing. by bobf (Monsignor) on Feb 17, 2006 at 05:28 UTC
That code should have generated a syntax error. You're missing a set of parentheses around the two conditions in the `if`: `if( (-e "data/$file.data") \|\| (-e "data/$otherfile.data") )` [download] Please refer to perlsyn for documentation on `if`, and perlop for documentation on `\|\|` and `or`.	[reply] [d/l] [select]
Re: The or thing. by planetscape (Chancellor) on Feb 17, 2006 at 07:06 UTC
PerlMonks has an excellent Tutorials page. In particular, the following will probably help you: Why you should use strict Use strict and warnings HTH, planetscape	[reply]
Re: The or thing. by spiritway (Vicar) on Feb 17, 2006 at 05:28 UTC
It seems to me that you need to put parentheses around the entire 'if' statement (both tests): `if ((-e "$file.data") \|\| (-e "$otherfile.data"))` When I run your test this way, I get the Hooray message. When I omit the enclosing parentheses, I can't even get the thing to run - so I'm wondering what it was that you were able to get working.	[reply] [d/l]
Re: The or thing. by strat (Canon) on Feb 17, 2006 at 09:01 UTC
Btw: if you just want to know if there is something with the name $file.data (e.g. a file, a directory, a link, a socket, ...), -e is correct. But if you want to know if it is a file and not a directory or socket or link or the like, you could better use -f, e.g `if (-f "data/$file.data" or -f "data/$otherfile.data) { ...` [download] see: perldoc -f -f if you also want to execute the script from other directories (e.g. because it is in $PATH or %PATH%, like ls or dir), then the script would try to find "data/$file.data" in a wrong place. If you want to keep ./data/ relatively to your script but don't want to write an absolute path, you can use FindBin, e.g. `use FindBin; my $dataPath = "$FindBin::Bin/data"; if (-f "$dataPath/$file.data" or -f "$dataPath/$otherdata.data") { ...` [download] this way is also often a good choise for Perl/CGI scripts because some webservers don't change there actual directory to the one your script is inside Best regards, perl -e "s>>F>e=>y)\martinF)stronat)=>print,print v8.8.8.32.11.32"	[reply] [d/l] [select]
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