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Full Discussion: awk construct unfamiliar to me
Top Forums UNIX for Dummies Questions & Answers awk construct unfamiliar to me Post 302678557 by agama on Saturday 28th of July 2012 10:42:43 AM
Old 07-28-2012
Awk's basic syntax is <expression> {<code-block>}. If expression evaluates to true, the associated block is executed. Either may be omitted; if the expression is omitted, true is assumed, and if the code block is omitted "print" is assumed. 1 evaluates as the expression to true, and so the single 1 imples 1 { print }.

---------- Post updated at 10:42 ---------- Previous update was at 10:37 ----------

Looking at the example you gave, this is how I would have written it:

Code:
awk '{for(i=2;i<=NF;i++)if($i==$1)$i=RS $i; print;}' input-file

It might be easier to see the difference if not smashed all on one line:

Code:
awk '
   {
      for( i=2; i<=NF; i++ )
         if( $i == $1)
            $i = RS $i; 
      print;
   }' input-file

Last edited by agama; 07-28-2012 at 11:44 AM.. Reason: typo
 

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LEARN ABOUT OSX

ucblinks

ucblinks(1B)					     SunOS/BSD Compatibility Package Commands					      ucblinks(1B)

NAME

       ucblinks - adds /dev entries to give SunOS 4.x compatible names to SunOS 5.x devices

SYNOPSIS

       /usr/ucb/ucblinks [-e rulebase] [-r rootdir]

DESCRIPTION

       ucblinks  creates symbolic links under the /dev directory for devices whose SunOS 5.x names differ from their SunOS 4.x names. Where possi-
       ble, these symbolic links point to the device's SunOS 5.x name rather than to the actual /devices entry.

       ucblinks does not remove unneeded compatibility links; these must be removed by hand.

       ucblinks should be called each time the system is reconfiguration-booted, after any new SunOS 5.x links that are needed have been  created,
       since the reconfiguration may have resulted in more compatibility names being needed.

       In  releases prior to SunOS 5.4, ucblinks used a  nawk rule-base to construct the SunOS 4.x compatible names. ucblinks no longer uses  nawk
       for the default operation, although  nawk rule-bases can still be specifed with the -e option.  The  nawk rule-base equivalent to the SunOS
       5.4 default operation can be found in /usr/ucblib/ucblinks.awk.

OPTIONS

       -e rulebase     Specify rulebase as the file containing nawk(1) pattern-action statements.

       -r rootdir      Specify rootdir as the directory under which dev and devices will be found, rather than the standard root directory /.

FILES

       /usr/ucblib/ucblinks.awk        sample rule-base for compatibility links

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWscpu			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       devlinks(1M), disks(1M), ports(1M), tapes(1M), attributes(5)

SunOS 5.10							    13 Apr 1994 						      ucblinks(1B)
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