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Full Discussion: awk, array indexing
Top Forums UNIX for Dummies Questions & Answers awk, array indexing Post 302678079 by neutronscott on Friday 27th of July 2012 07:54:37 AM
Old 07-27-2012
Just the indexing? I will try to explain all of it.

Firstly, it is often (and better) written:

Code:
nawk -F= '!a[$1]++' filename

Each record (a line here) is split into fields. The first field is addressed with $1, the second with $2, and so on. The entire record is $0. So it uses $1 as the index into the array called a. Stored there is the count of occurances (the ++ operator increments the value). The first time it is seen though, it evaluates as 0. (It returns 0 but is then set to 1, called post-increment). So the ! operator will negate that. So it will only print the first line where $1 is unique, because each successive iteration of that same $1 will then become 0 after !.
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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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