Strange result of eval, how does eval really work with ssh?


 
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Old 05-05-2011
I'm not sure what you are trying to accomplish, but it smells dangerous.
In here:
Quote:
echo "ls
ls -l" | while read line;do
eval $line
done
you would call 'eval <file>' for each file on the remote system. You almost certainly don't want to do that.
If there was a file named 'rm -rf $dir' in that dir, with your loop you'd execute just that! It's not good to use eval unless you're sure that eval's argument is fixed and you know what it is.

So, to answer your question: It's not the strange behavior of eval, it's the strange construct that you cooked. Look at the contents of the directory. If you had a file named 'break' in that dir, you'd end the loop when 'eval break' gets called.
 
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Perl::Critic::Policy::BuiltinFunctions::ProhibitStringyEUser3Contributed Perl DocumePerl::Critic::Policy::BuiltinFunctions::ProhibitStringyEval(3)

NAME
Perl::Critic::Policy::BuiltinFunctions::ProhibitStringyEval - Write "eval { my $foo; bar($foo) }" instead of "eval "my $foo; bar($foo);"". AFFILIATION
This Policy is part of the core Perl::Critic distribution. DESCRIPTION
The string form of "eval" is recompiled every time it is executed, whereas the block form is only compiled once. Also, the string form doesn't give compile-time warnings. eval "print $foo"; # not ok eval {print $foo}; # ok CONFIGURATION
There is an "allow_includes" boolean option for this Policy. If set, then strings that look like they only include a single "use" or "require" statement (with the possible following statement that consists of a single number) are allowed. With this option set, the following are flagged as indicated: eval 'use Foo'; # ok eval 'require Foo'; # ok eval "use $thingy;"; # ok eval "require $thingy;"; # ok eval "use $thingy; 1;"; # ok eval "require $thingy; 1;"; # ok eval 'use Foo; blah;'; # still not ok eval 'require Foo; 2; 1;'; # still not ok eval 'use $thingy;'; # still not ok eval 'no Foo'; # still not ok If you don't understand why the number is allowed, see Perl::Critic::Policy::ErrorHandling::RequireCheckingReturnValueOfEval. This option inspired by Ricardo SIGNES' Perl::Critic::Policy::Lax::ProhibitStringyEval::ExceptForRequire. SEE ALSO
Perl::Critic::Policy::ControlStrucutres::RequireBlockGrep Perl::Critic::Policy::ControlStrucutres::RequireBlockMap AUTHOR
Jeffrey Ryan Thalhammer <jeff@imaginative-software.com> COPYRIGHT
Copyright (c) 2005-2011 Imaginative Software Systems. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. The full text of this license can be found in the LICENSE file included with this module. perl v5.16.3 2014-06-09 Perl::Critic::Policy::BuiltinFunctions::ProhibitStringyEval(3)