Bash scripts for text file manipulations

I used these scripts in an environment which had a lot of text files. Too much to work on them manually.
They do some basic tasks like inserting lines, merging text files and so on with all files contained in the directory "files".

The first script inserts the content of another text file at the beginning.

#!/bin/bash
for i in ./files/*
do
  cat sampletext.txt > ${i}_tmp
  cat $i >> ${i}_tmp
  mv ${i}_tmp $i
done
exit

Find a certain line with grep and extract the line number. Then delete all lines from this line(including) until line 2000.

#!/bin/bash
for i in ./files/*
do
  LINENUMBER=`grep -n "some text" $i | sed 's/:.*//'`
  sed -i -e "$LINENUMBER,2000d" $i
done
exit

Find the html tag <h1> and extract the content of it.
Put it into the html tag <title>.

#!/bin/bash
for i in ./files/*
do
  H1=`grep "<h1>" $i | sed -e 's/^.*<h1>//' | sed -e 's/<\/h1.*$//'`
  sed -i -e "s/<title>.*<\/title>/<title>$H1<\/title>/" $i
done
exit

Take the first 20 lines, write them into a temporary file.
Then append a line at the end and finally take the content from the original file from line 22(including) and append it as well.

#!/bin/bash
for i in ./files/*
do
 head -n20 $i > ${i}_tmp
 echo -e "some text" >> ${i}_tmp
 tail -n +22 $i >> ${i}_tmp
 mv ${i}_tmp $i
done
exit

Also very helpful for those operations is the command "tac".
It reverses all lines so that the file starts with the last line.