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Re: Re: PIPE problem

by graq (Curate)
on Feb 22, 2003 at 07:31 UTC ( [id://237698]=note: print w/replies, xml ) Need Help??


in reply to Re: PIPE problem
in thread PIPE problem

I'm not convinced that you are correct:  perl -e '$foo="tada;";print "$foo\n"'

Your answer has nothing to do with the | (pipe) causing the error. Whether there is a table to describe or not, does not take away the fact that you can have as many semi-colons inside quotes as you like, Perl will not mind.

[EDIT]
Boy, there I was trying to make things clearer, and I muddy them, sorry.

suekawar, maybe your problem stems from a lack of documentation. I found nowhere on PerlMonks or Perldoc.com that explains how qx works in any simple terms.

perl -e ' > $foo = qx[ echo "Me Graq!" ]; > print "$foo"; > ' Me Graq!
Try reading http://www.perldoc.com/perl5.8.0/pod/perlop.html#Quote-and-Quote-like-Operators.

VSarkiss, I was trying to put across that for someone confused between system, qq and qx your answer might not be so clear.

<a href="http://www.graq.co.uk">Graq</a>

Replies are listed 'Best First'.
Re: Re: Re: PIPE problem
by MarkM (Curate) on Feb 22, 2003 at 17:05 UTC

    You are missing a critical point... qx/COMMANDLINE/ or system("COMMANDLINE") invokes /bin/sh with the -c option like so: (on WIN32, this is of course a little different)

    execl("/bin/sh", "-c", COMMANDLINE);

    The quotes in COMMANDLINE are not being ignored or parsed by Perl. They are being handled by /bin/sh. Notice that at a /bin/sh prompt, if you were to type:

    $ echo "Hello World" Hello World

    For the original example, the poster was trying to do:

    $ SQLCOMMAND; | sqlplus ...

    It should have been:

    $ echo "SQLCOMMAND;" | sqlplus ...

    The shell uses the quotes to group arguments. The quotes are not passed through to the command (again, under WIN32, this is a little more convoluted).

    The original problem posted was two-fold. First, as the initial responder suggested, the poster should have used 'echo "SQLCOMMAND;"' not 'SQLCOMMAND;'. As a later responder suggested, the poster should not be using both qx// and system() as both will execute the command. Either system() should be used if the output does not need to be intercepted, or qx// should be used if the output does need to be intercepted.

Re: Re: Re: PIPE problem
by suekawar (Novice) on Feb 24, 2003 at 15:09 UTC
    thanks for the help

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