Shell Programming and Scripting

#!/bin/bash

for prog in `cat toinstall | grep -vP "^#" | grep -vP "^$"`
do
    TEMPVAL=$(`dpkg -l | awk '{ if ($2 == "${prog}") print $2}'`)
    if [  "$TEMPVAL" == "" ]
    then
    sudo apt-get install -y $prog
    fi
done

+ for prog in '`cat toinstall | grep -vP "^#" | grep -vP "^$"`'
+++ dpkg -l
+++ awk '{ if ($2 == "${prog}") print $2}'
+ TEMPVAL=
+ '[' '' == '' ']'
+ sudo apt-get install -y vim

TEMPVAL=$(dpkg -l | awk '{ if ($2 == "'${prog}'") print $2}')

TEMPVAL=$(dpkg -l | awk '{ if ($2 == prog) print $2}' prog="${prog}")

awk '{ if ($2 == "'"$prog"'") print $2}'

awk '$2 == "'"$prog"'" {print $2}'

awk -v VAR="$prog" '$2 == VAR { print $2 }'

$ STR="hello 'world'"
$ awk 'BEGIN { print "'$STR'" }'
awk: BEGIN { print "hello
awk:               ^ unterminated string
$

 VAR="this will barf'"
# subsitute in the shell and it barfs, taking the extra ' as perl syntax
$ perl -e "print '$VAR', "\n";'
Can't find string terminator '"' anywhere before EOF at -e line 1.
# do it properly and it will not.
$ perl -e 'print shift, "\n"' "$VAR"
this will barf'
$