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With double quotes

The following command

$ cat ./multi_meta | jq .Partitions[].DocCount | perl -lne "$x += $_; END{ print $x;}"

gives me a syntax error：

syntax error at -e line 1, near "+="
Execution of -e aborted due to compilation errors.

With single quotes

I get the correct result with

$ cat ./multi_meta | jq .Partitions[].DocCount | perl -lne '$x += $_; END{ print $x;}'

Why?

Stefan Becker
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infantcoder
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2 Answers2

2

Because with double quotes, the whole string is passed through your shell's variable expansion mechanisms before the Perl compiler sees the code. And as you don't have shell variables called $x or $_, the Perl compiler sees this:

+= ; END{ print ;}

With single quotes, your Perl variables are protected from expansion until the Perl compiler can see them.

Dave Cross
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0

I think the problem is your shell expanding $x as it was a shell variable and not as a perl variable, the solution should be escape $ like this \$.

sergiotarxz
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