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Execution problem with perl

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# 1  
Old 03-10-2010
Execution problem with perl
I got the below error when using the below code...it seem that perl interpret the "'" in the middle and therefore the pipe is not finished.

Code:
perl -wle '
@a=`who| perl -wlane 'print \$F[0];' | sort -u` ;
chomp @a ;
print @a;
'


Code:
the error message in cygwin is:-
perl: No match.
 | sort -u`;chomp @a ; print @a;: Command not found.

Code:
error message on Solaris is:-
Can't find string terminator "`" anywhere before EOF at -e line 2.
bash :  | sort -u
`; chomp @a ;
print @a ;
: command not found

even I try qx// instead of `` without any use.SmilieSmilieSmilie


Thanks in advance.

BR
# 2  
Old 03-10-2010
In your original version, the shell is closing and reopening the single-quoted string. Try:
Code:
perl -wle '
@a=`who| perl -wlane '\''print \$F[0];'\'' | sort -u` ;
chomp @a ;
print @a;
'

Whenever you need to embed single-quotes in a single-quoted string, you need to first close the single-quoted string, add a backslash-escaped single-quote, then reopen the single quoted string immediately afterwards (all of this is to appease the shell's parser, it has nothing to do with perl).

So
Code:
'

becomes
Code:
'\''

for every instance of a single quote you'd like to place inside a single-quoted string.

Regards,
Alister
# 3  
Old 03-10-2010
Try this:

Code:
@a = qx(who| perl -wlane \47print \$F[0];\47 | sort -u);

Why don't you write it all in Perl (without embedding code)?
# 4  
Old 03-10-2010
Quote:
Originally Posted by radoulov
Try this:

Code:
@a = qx(who| perl -wlane \47print \$F[0];\47 | sort -u);

Why don't you write it all in Perl (without embedding code)?
I tried it with the same error this was one of my tries. but with out any use.Smilie actually the system is ignoring the 'print \$F[0]' and print all the who command o/p.

# 5  
Old 03-10-2010
Hm ...

Code:
$ who
drado      pts/1        Mar 10 20:21    (xxx)
drado      pts/2        Mar 10 20:25    (xxx)
$ perl -wle '
  @a = qx(who| perl -wlane \47print \$F[0];\47 | sort -u);
  chomp @a;
  print @a;
'
drado

It works for me.
Last edited by radoulov; 03-10-2010 at 03:24 PM..
# 6  
Old 03-10-2010
Quote:
Originally Posted by alister
In your original version, the shell is closing and reopening the single-quoted string. Try:
Code:
perl -wle '
@a=`who| perl -wlane '\''print \$F[0];'\'' | sort -u` ;
chomp @a ;
print @a;
'

Whenever you need to embed single-quotes in a single-quoted string, you need to first close the single-quoted string, add a backslash-escaped single-quote, then reopen the single quoted string immediately afterwards (all of this is to appease the shell's parser, it has nothing to do with perl).

So
Code:
'

becomes
Code:
'\''

for every instance of a single quote you'd like to place inside a single-quoted string.

Regards,
Alister

Sorry Alister but the problem as in radoulov solution
# 7  
Old 03-10-2010
I would write something like this:

Code:
perl -le'
  $_{(split)[0]} = 1 for qx(who);
  print sort keys %_;
  '
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