syntax error near unexpected token `|' Perl code

Question

I am trying to execute this in my perl script

my $command = `ps -p  $pidnumber |  wc -l`;

but when I run the script it show me something like this:

sh: -c: line 1: syntax error near unexpected token `|'

sh: -c: line 1: ` | wc -l'

Which would it may to be the error?

Where is $pidnumber coming from? Might it have a newline appended to it? — RickF
– RickF, Commented Apr 2, 2013 at 17:13

mob · Accepted Answer · 2013-04-02 17:16:19Z

1

Does $pidnumber end with a new line? See the chomp function.

answered Apr 2, 2013 at 17:16

mob

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Comments

Miguel Prz · Accepted Answer · 2013-04-02 17:54:25Z

1

try print before execute the command, because $pidnumber may have something strange:

my $command_str = "ps -p  $pidnumber |  wc -l";
print $command_str, "\n";
my $command = qx!$command_str!;

as @mob said, use chomp if newline appears in the print sentence.

answered Apr 2, 2013 at 17:54

Miguel Prz

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use Data::Dumper; local $Data::Dumper::Useqq = 1; print(Dumper($command_str)); for more useful at finding oddities, especially trailing newlines.

Vorsprung · Accepted Answer · 2013-04-02 18:47:03Z

1

I agree with the other answers that an extra newline before the pipe is quite possibly the cause

But the command doesn't really need the pipe!

force the quoted command to return it's value as a list and then get the length of the list and you've got the wc -l "line count"

my $command_str = "ps -p  $pidnumber";
my $linecount = () = qx!$command_str!;

answered Apr 2, 2013 at 18:47

Vorsprung

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