Shell Programming and Scripting

#!/usr/bin/env bash

# @(#) s1	Demonstrate finding common lines, special case, grep.

# Utility functions: print-as-echo, print-line-with-visual-space, debug.
# export PATH="/usr/local/bin:/usr/bin:/bin"
pe() { for _i;do printf "%s" "$_i";done; printf "\n"; }
pl() { pe;pe "-----" ;pe "$*"; }
edges() { local _f _n _l;: ${1?"edges: need file"}; _f=$1;_l=$(wc -l $_f);
  head -${_n:=3} $_f ; pe "--- ( $_l: lines total )" ; tail -$_n $_f ; }
db() { ( printf " db, ";for _i;do printf "%s" "$_i";done;printf "\n" ) >&2 ; }
db() { : ; }
C=$HOME/bin/context && [ -f $C ] && $C grep

MAIN=${1-data1}
shift
PATS=${1-data2}

pl " Input data files $MAIN $PATS:"
edges $MAIN
pe
edges $PATS

pl " Results:"
grep -f $PATS $MAIN

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 5.0.8 (lenny) 
bash GNU bash 3.2.39
grep GNU grep 2.5.3

-----
 Input data files data1 data2:
a,1
b,2
c,343
--- ( 6 data1: lines total )
d,343
e,4343
f,4544

a,
d,
e,
--- ( 3 data2: lines total )
a,
d,
e,

-----
 Results:
a,1
d,343
e,4343