11-26-2012
p1 is used to store the value of the first field. Since this is done at the end of each line processing, it becomes the previous value of the first field for the current line.
Quote:
Is prev a built-in variable?
No. In
awk, the built-in variables are all upper-case words.
prev is used to store the line made up by appending segments of the lines which have common first fields. After printing each made-up line, we need to nullify the variable to make it ready for the next line to be made up.
And the cryptic line does what you thought it does. If
prev"" (
prev is not-null) is true, then we must be having at least 1 line in
prev so we need to append a
, (
FS - field separator, comma in this case, and that's a special/built-in
awk variable) and the substring of the line from the second field onwards. Else if
prev is null, then it must be the first time since printing the last
prev. So, just assign the current line (
$0) to
prev.
And, I think you've understood rest of the things.
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LEARN ABOUT DEBIAN
dpkg-awk
DPKG-AWK(1) General Commands Manual DPKG-AWK(1)
NAME
dpkg-awk - Utility to read a dpkg style db file
SYNOPSIS
dpkg-awk [(-f|--file) filename] [(-d|--debug) ##] [(-s|--sort) list] [(-rs|--rec_sep) ??] '<fieldname>:<regex>' ... -- <out_fieldname> ..
DESCRIPTION
dpkg-awk Parses a dpkg status file (or other similarly formatted file) and outputs the resulting records. It can use regex on the field
values to limit the returned records, it can also be told which fields to output, and it can sort the matched fields.
OPTIONS
-f filename
--file filename
The file to parse. The default is /var/lib/dpkg/status.
-d [#]
--debug [#]
Each time this is specified, it increased the debug level.
-s field(s)
--sort field(s)
A space or comma separated list of fields to sort on.
-n field(s)
--numeric field(s)
A space or comma separated list of fields that should be interpreted as numeric in value.
-rs ??
--rec_sep ??
Output this string at the end of each output paragraph.
-h
--help Display some help.
fieldname
The fields from the file, that are matched with the regex given. The fieldnames are case insensitive.
out_fieldname
The fields from the file, that are output for each record. If the first field listed begins with ^, then the list of fields that
follows will NOT be output.
BUGS
Be warned that the author has only a shallow understanding of the dpkg packaging system, so there are probably tons of bugs in this pro-
gram.
This program comes with no warranties. If running this program causes fire and brimstone to rain down upon the earth, you will be on your
own.
This program accesses the dpkg database directly in places, querying for data that cannot be gotten via dpkg.
AUTHOR
Adam Heath <doogie@debian.org>
DEBIAN
Debian Utilities DPKG-AWK(1)