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sed to add a line to a file after a string match

A simple script to find a pattern in a file and than add a line to the file.

1. When I needed to add a new button to all pages in this site, I used this script.
2. The requirement is simple: per a given file, check if an input string is found in the file. If it does, add the new line after the line with the match.
3. I do it on all files by the following command:
find . -name "*.html" | xargs -n1 | xargs -i= ~/bin/add_html_button.unx =


4. The script is shown below:
#!/bin/bash

sed '/match string/ a new string for new added line ' $1 > Tmp
\mv -f Tmp $1



5. Recently I saw that this can be done in one step:
   In this example I put perl line in remark by adding # at the beginning of the line.
   

sed -i "s/^\(\&ads_0001;\)/#\1/" Home_2/udp_code.pl


6. If any of the strings contains forward slash, one can use another character as the replace separator.
   sed -i "s,^\(\&ads_0001;\),#\1/," Home_2/udp_code.pl
   sed -i "s;OLD_SWITCH;$HTML_SWITCH;" Home_2/udp_code.pl
   
   

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