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Full Discussion: Two curious questions
Top Forums Shell Programming and Scripting Two curious questions Post 302709647 by Corona688 on Wednesday 3rd of October 2012 11:56:55 AM
Old 10-03-2012
a) There is a limit to how much stuff you can cram in a single shell variable. On some systems, this can be as small as a screenful or so, so don't go overboard.

b) If you're doing awk | awk | sed | cut | kitchen | sink, you probably could have done that all in one awk and saved yourself a lot of bother and CPU time. You don't need to use awk twice here:

Code:
awk '{ sum += $2 } END { print sum }' inputfile

c) That's also a useless use of cat, since awk does not need cat's help to read a file. You can use it as shown above, listing the filename on the end.

To answer question 2, there's actually a few ways to set more than one variable at once. read is a particularly flexible way of doing so. It helps if you know how many are coming, though, or can convince certain ones to come first. Everything you didn't list will get crammed into the last variable you list.

Code:
read SUM NUMBERS <<EOF
`awk '{ sum += $2; A[++L]=$0 } END { print sum ; for(N=1; N<=L; N++) print A[N]}' inputfile`
EOF

I saved all the numbers in the awk array A so I could print them later. This lets me print the sum first, and then the rest, letting me pick the sum out from the front with read.

You could also do
Code:
set -- `awk '{ sum += $2; A[++L]=$0 } END { print sum ; for(N=1; N<=L; N++) print A[N]}' inputfile`

SUM=$1
shift
REST="$*"

This User Gave Thanks to Corona688 For This Post:
jamie_123
 

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LEARN ABOUT DEBIAN

xmlstarlet

XMLSTARLET(1)							 xmlstarlet Manual						     XMLSTARLET(1)

NAME

       xmlstarlet - command line XML/XSLT toolkit

SYNOPSIS

       xmlstarlet [<options>] [<command>] [<cmd-options>]

INTRODUCTION

       XMLStarlet is a set of command line utilities (tools) which can be used to transform, query, validate, and edit XML documents and files us-
       ing simple set of shell commands in similar way it is done for plain text files using UNIX grep, sed, awk, diff, patch, join, etc commands.
       This  set of command line utilities can be used by those who deal with many XML documents on UNIX shell command prompt as well as for auto-
       mated XML processing with shell scripts.

OPTIONS

       --version
	      Display the version of xmlstarlet.

       --help Display help.

COMMANDS

       Type: xmlstarlet <command> --help <ENTER> for command help

       Available commands include:

       ed (or edit)
	      Edit/update XML document(s).

       sel (or select)
	      Select data or query XML document(s) (XPATH, etc).

       tr (or transform)
	      Transform XML documents(s) using XSLT.

       val (or validate)
	      Validate XML document(s) (well-formed/DTD/XSD/RelaxNG).

       fo (or format)
	      Format XML document(s).

       el (or elements)
	      Display element structure of XML document.

       c14n (or canonic)
	      XML canonicalization.

       ls (or list)
	      List directory as XML.

       esc (or escape)
	      Escape special XML characters.

       unesc (or unescape)
	      Unescape special XML characters.

       pyx (or xmln)
	      Convert XML into PYX format (based on ESIS - ISO 8879).

       p2x (or depyx)
	      Convert PYX into XML.

REFERENCES

       XMLStarlet is a command line  toolkit  to  query/edit/check/transform  XML  documents  (for  more  information  see  http://xmlstar.source-
       forge.net/).

AUTHOR

       Mikhail Grushinskiy.

																     XMLSTARLET(1)
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