Shell Programming and Scripting

#!/bin/sh
cp ch25.txt ch25.fn.tex
n=`grep -c '^\[' ch25_footnotes.txt`

for i in {1..$n}
do
        `grep '^\[$i\]' ch25_footnotes.txt > temp`
        r=`awk -F] '{print $2}' temp`
        `sed 's/\[$i\]/\\footnote{$r}/' ch25.fn.tex`
done

for i in {1..5}
do 
    echo $i; #to make sure the for loop was working as expected.
    
    str="grep '^\[$i\]' ch25_footnotes.txt"; #I saved the whole thing as a string, which DOES 
                                             #interpret $i as a variable.  If I were to echo that 
                                             #command, it would have a number there 
                                             #rather than a $i.
   
    eval $str; #this actually runs the grep command
done

#!/bin/sh
cp ch25.txt ch25.fn.tex
n=`grep -c '^\[' ch25_footnotes.txt`
echo $n

#for i in {1..n};  ### This syntax was not working, for some reason

for ((i=1; i <= n ; i++))
do
        str="grep '^\[$i\]' ch25_footnotes.txt > temp"
#      echo $str
        eval $str
        r=`awk -F] '{print $2}' temp`
#      echo $r ## Up to here, things work as expected.
        str2="sed 's/\[$i\]/\\\footnote{$r}/' ch25.fn.tex"
        eval $str2
done

$
$ cat ch25.txt
First there was nothing. Then there was Calvin[1].
blah blah blah
blah blah blah
"On a long enough timeline, the survival rate for everyone drops to zero" [2].
blah blah blah
"Dr. Livingstone, I presume?" [3]
blah blah blah
$
$ cat footnotes.txt
[1] A memorable quote from Bill Waterson's Calvin and Hobbes.
[2] Spoken by Tyler Durden, in Chuck Palahniuk's "Fight Club".
[3] By Henry Morton Stanley, on meeting Dr. David Livingstone near Lake Tanganyika on Nov. 10th, 1871.
$
$
$ perl -ne 'BEGIN {
>   open(FN,"footnotes.txt");
>   while(<FN>) {chomp; $fnote{$1}=$2 if (/(\[\d+\]) (.*)/)}
>   close(FN)}
> chomp;
> if (/(.*?)(\[\d+\])/) {print "$1\\footnote{$fnote{$2}}\n"}
> else {print $_,"\n"}' ch25.txt
First there was nothing. Then there was Calvin\footnote{A memorable quote from Bill Waterson's Calvin and Hobbes.}
blah blah blah
blah blah blah
"On a long enough timeline, the survival rate for everyone drops to zero" \footnote{Spoken by Tyler Durden, in Chuck Palahniuk's "FightClub".}
blah blah blah
"Dr. Livingstone, I presume?" \footnote{By Henry Morton Stanley, on meeting Dr. David Livingstone near Lake Tanganyika on Nov. 10th, 1871.}
blah blah blah
$
$

awk 'FNR==NR{id[$1]="{"substr($0,length($1)+2,length($0))"}";next}
{a=$0;b=match($0,/\[[0-9]+\]/);
if(b>0){
c=substr($0,RSTART,RLENGTH);o=substr($0,1,b-1);print o"\\footnote"id[c]
}
else print
}' footnotes.txt ch25.txt