UNIX for Dummies Questions & Answers

$ABC.1
XYGHGHGHHG
$ABC.2
RSTUVBWBB
$ABC.3
87908787798798
$QRS.5
$RST.6
679707097
$LmN.4
hgkhgh
$QRS.5
$ABC.9

sed -n "/^\$/p" file

$QRS.5
$RST.6

$QRS.5
$ABC.9

sed -n '/^\$/{N;/\n\$/p;}' file

awk '/^\$/{if(!p)x=$0;p++}!/^\$/{p=0}p==2{print x}p>1' file

# cat infile
$ABC.122
XYGHGHGHHG
$ABC.222
RSTUVBWBB
$ABC.3
$ABC.4
RSTUVBWBB
$ABC.5
$ABC.6
$ABC.7
87908787798798
$QRS.8
$RST.9
$RST.10
$RST.11
679707097
$QRS.12
$QRS.13
$RST.14
$RST.15
$RST.16
hgkhgh
$QRS.17
$QRS.18
$ABC.19
$ABC.20
$ABC.21
$ABC.22
sdasdfadwe
$QRS.23
$QRS.24
$ABC.25
$ABC.26
$ABC.27
$ABC.28
$ABC.29
sdasdfadwe
 
$QRS.30
$QRS.31
$ABC.32
$ABC.33
$ABC.34
$ABC.35
$ABC.36
 
 
ddp
sdasdfadwe
 
$ABC.37
$ABC.38
$ABC.39
$QRS.40
$QRS.41
$ABC.42
$QRS.43
$QRS.44
$QRS.45
$QRS.46
$QRS.47
$QRS.48
 
$QRS.49
$ABC.50
$ABC.51

# sed -e '/^\$/N;' -e 's/.*\n[^\$]*$//;/\$/n;/\$/n;/\$/n;/\$/n;/\$/n;;s/^[^\$]*//' infile
 
 
$ABC.3
$ABC.4
 
$ABC.5
$ABC.6
$ABC.7
 
$QRS.8
$RST.9
$RST.10
$RST.11
 
$QRS.12
$QRS.13
$RST.14
$RST.15
 
$RST.16
$QRS.17
$QRS.18
$ABC.19
$ABC.20
$ABC.21
 
$ABC.22
$QRS.23
$QRS.24
$ABC.25
$ABC.26
$ABC.27
$ABC.28
$ABC.29
 
 
$QRS.30
$QRS.31
$ABC.32
$ABC.33
$ABC.34
$ABC.35
$ABC.36
 
 
 
 
$ABC.37
$ABC.38
$ABC.39
$QRS.40
$QRS.41
$ABC.42
$QRS.43
$QRS.44
$QRS.45
$QRS.46
$QRS.47
$QRS.48
 
$QRS.49
$ABC.50
$ABC.51

#!/usr/bin/env bash

# @(#) s1	Demonstrate treating lines as fields in awk for counting.

# Section 1, setup, pre-solution.
# Infrastructure details, environment, commands for forum posts. 
# Uncomment export command to run script as external user.
# export PATH="/usr/local/bin:/usr/bin:/bin"
set +o nounset
pe() { for i;do printf "%s" "$i";done; printf "\n"; }
pl() { pe;pe "-----" ;pe "$*"; }
LC_ALL=C ; LANG=C ; export LC_ALL LANG
pe ; pe "Environment: LC_ALL = $LC_ALL, LANG = $LANG"
pe "(Versions displayed with local utility \"version\")"
c=$( ps | grep $$ | awk '{print $NF}' )
version >/dev/null 2>&1 && s=$(_eat $0 $1) || s=""
[ "$c" = "$s" ] && p="$s" || p="$c"
version >/dev/null 2>&1 && version "=o" $p printf specimen sed awk
set -o nounset
pe

FILE=${1-data1}

# Display sample of data file, with head & tail as a last resort.
pe " || start [ first:middle:last ]"
specimen 7 $FILE \
|| { pe "(head/tail)"; head -n 5 $FILE; pe " ||"; tail -n 5 $FILE; }
pe " || end"

# Section 2, solution.
pl " Results:"
sed 's/^[^\$].*//' $FILE |
awk '
BEGIN	{ RS = "" ; FS = "\n" ; ORS = "\n\n" }
# Uncomment following lines to see number of fields in multi-line group
# NF > 1	{ print " Input line is " NR " number of fields is " NF }
NF > 1	{ print $0 }
' |
specimen 

# Section 3, post-solution, check results, clean-up, etc.

exit 0

% ./s1

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 2.6.26-2-amd64, x86_64
Distribution        : Debian GNU/Linux 5.0 
GNU bash 3.2.39
printf - is a shell builtin [bash]
specimen (local) 1.17
GNU sed version 4.1.5
GNU Awk 3.1.5

 || start [ first:middle:last ]
Whole: 7:0:7 of 13 lines in file "data1"
$ABC.1
XYGHGHGHHG
$ABC.2
RSTUVBWBB
$ABC.3
87908787798798
$QRS.5
$RST.6
679707097
$LmN.4
hgkhgh
$QRS.5
$ABC.9
 || end

-----
 Results:
Whole: 5:0:5 of 6 lines in file "-"
$QRS.5
$RST.6

$QRS.5
$ABC.9