awk: syntax for "if (array doesn't contain a particular index)" Post: 302703581

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Top Forums UNIX for Dummies Questions & Answers awk: syntax for "if (array doesn't contain a particular index)" Post 302703581 by beca123456 on Thursday 20th of September 2012 03:30:37 AM

09-20-2012

Registered User

Thanks agama for your explanations !

Quote:

In my opinion, it's bad form to reference field values (e.g. $1) in a function. Better to pass in the contents of the field that you wish to operate on.

I don't get it. What is the difference between the field value (e.g. $1) and the content of the field? Is it not the same at the end?

I managed to go farther with your code and added a for loop after to increment the start position:

Code:

BEGIN {
        xtab["11"]="a";
        xtab["12"]="b";
        xtab["13"]="c";
    }
  
    # accepts word and starting offset 
    function xlate( w, start)
    {
        xw = ""
        n = substr(w, start, 2)    # seed n with first pair 
        while( n != "" )
        {
            xw = xw (n in xtab ? xtab[n] : "X")
            start = start + 2;
            n = substr(w, start, 2)    # look ahead to next; exit loop if at end
        }
        return xw
    }
    { for(i=1; i<=2; i++)
   	  print xlate($1, i)
    }

it returns:

Code:

abc
aXX
abX
aXX

However, if I want farther to extend the code and refer to this field, for example to print only string without X (as a beginning), is there any way to use again the term "$1" in the rest of the script?
Even when I re-assign the value to $1 it doesn't work!

Code:

BEGIN {
        xtab["11"]="a";
        xtab["12"]="b";
        xtab["13"]="c";
    }
  
    # accepts word and starting offset 
    function xlate( w, start)
    {
        xw = ""
        n = substr(w, start, 2)    # seed n with first pair 
        while( n != "" )
        {
            xw = xw (n in xtab ? xtab[n] : "X")
            start = start + 2;
            n = substr(w, start, 2)    # look ahead to next; exit loop if at end
        }
        return xw
    }

    { for(i=1; i<=2; i++)
   	  print xlate($1, i)
    }

    { for(i=1; i<=2; i++)
    		print $1 = xlate($1, i)
                if($1 !~ /X/){
            	    print $1
            	    }
     }

Last edited by beca123456; 09-20-2012 at 04:49 AM..

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xtab

exports(4)						     Kernel Interfaces Manual							exports(4)

NAME

       exports, xtab - directories to export to NFS clients

SYNOPSIS

DESCRIPTION

       The file is obsolete and has been replaced by the new NFS file Please see dfstab(4) for more details.

       The file is also obsolete and has been replaced by the new NFS file Please see sharetab(4) for more details.

       The and the files are no longer used to export NFS directories.	Any modifications made to these files will have no impact on NFS.

       These manpages will be removed from future releases of HP-UX.

AUTHOR

       was developed by Sun Microsystems, Inc.

FILES

       list of commands to be executed at boot time

       system record of shared file systems

       list of hostnames

       list of network groups

       network information

       script that executes
	      command.

SEE ALSO

       share(1M), mountd(1M), nfsd(1M), dfstab(4), hosts(4), netgroup(4), networks(4), sharetab(4).

								  TO BE OBSOLETED							exports(4)

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xtab