UNIX for Beginners Questions & Answers

Dog        Cat
              fido       sneaky
             dopey      poptart
             ears       whisker
             barky      herd

Dog        Cat
fido       sneaky
dopey      poptart
ears       whisker
barky      herd

awk -v header="Dog" '
BEGIN { FS=" "; c=0 }
NR == 1 { for (i=1;i<=NF;i++) { if ($i==header) { c=i }} }
NR > 1 && c>0 { print $c }
' dogs.log

#!/bin/ksh
echo 'Original code results:'
awk -v header="${1:-Dog}" '
BEGIN { FS=" "; c=0 }
NR == 1 { for (i=1;i<=NF;i++) { if ($i==header) { c=i }} }
NR > 1 && c>0 { print $c }
' dogs.log
echo "*** Exit status: $?"

printf '\nModified code results:\n'
awk -v header="${1:-Dog}" '
NR == 1 {
	for(i = 1; i <= NF; i++)
		if($i == header) {
			c = i
			next
		}
	printf("Header \"%s\" not found.\n", header)
	exit 1
}
{	print $c
}' dogs.log
echo "*** Exit status: $?"

chmod +x tester

./tester

Original code results:
fido
dopey
ears
barky
*** Exit status: 0

Modified code results:
fido
dopey
ears
barky
*** Exit status: 0

./tester Cat

Original code results:
sneaky
poptart
whisker
herd
*** Exit status: 0

Modified code results:
sneaky
poptart
whisker
herd
*** Exit status: 0

./tester Horse

Original code results:
*** Exit status: 0

Modified code results:
Header "Horse" not found.
*** Exit status: 1

#!/usr/bin/env bash

# @(#) s1       Demonstrate manipulation of CSV data.
# csvtool, Debian repository, and:
# https://github.com/Chris00/ocaml-csv
#
# align: http://kinzler.com/me/align/

# Utility functions: print-as-echo, print-line-with-visual-space, debug.
# export PATH="/usr/local/bin:/usr/bin:/bin"
LC_ALL=C ; LANG=C ; export LC_ALL LANG
pe() { for _i;do printf "%s" "$_i";done; printf "\n"; }
pl() { pe;pe "-----" ;pe "$*"; }
em() { pe "$*" >&2 ; }
db() { ( printf " db, ";for _i;do printf "%s" "$_i";done;printf "\n" ) >&2 ; }
db() { : ; }
C=$HOME/bin/context && [ -f $C ] && $C csvtool align

FILE=${1-data1}

pl " Input data file $FILE:"
cat $FILE

pl " Results:"
sed 's/  */,/g' $FILE |
tee f1 |
csvtool namedcol Cat,Dog - |
align -s /,

exit 0

$ ./s1

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 3.16.0-4-amd64, x86_64
Distribution        : Debian 8.4 (jessie) 
bash GNU bash 4.3.30
csvtool - ( /usr/bin/csvtool, 2014-08-06 )
align 1.7.0

-----
 Input data file data1:
Dog        Cat
fido       sneaky
dopey      poptart
ears       whisker
barky      herd

-----
 Results:
Cat     Dog
sneaky  fido
poptart dopey
whisker ears
herd    barky