How to replace text between two markers in a file with a section of text from another file?

Say I had a block of text in the ~/.bashrc:

#~/.bashrc
# ...some commands...

# aliases
alias suicide='sudo rm -rf /'
# end aliases

# other commands

I wish to replace that block of text with some other text contained between two markers in another file: stuff-to-place-in-bashrc.txt

# stuff-to-place-in-bashrc.txt
# ...stuff...

# aliases
alias ldir='ls * -d'
alias ithinklifeisworthliving='echo all good'
# end aliases

# ...more stuff...

I’ve tried

 sed -ne 's/# aliasess+(.*)s+# end aliases/1/' stuff-to-place-in-bashrc.txt

But I’m really swinging in the dark here. Could someone help me out?

1. How do I extract the text from the stuff-to-place-in-bashrc.txt?
2. How do I replace the other section in ~/.bashrc with the extracted text from question 1?

Edit

Thanks for the updates guys, those wondering why i would want something like this:

allows for cherry-picked updates to script files without overwritting user-made additions. useful for shared and frequently updated standard operating environments (like my last job at Tyro that coded with XP).

go crazy guys.

Answers:

Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

Ed is the standard editor, because you can use it to develop ed scripts and let it do its work, as you tested before, interactively. For small files like .bashrc or any code text, ed is performant because it reads the whole file in one rush and works with the buffer. For the same reason you should not use ed for big files like log files.

But with an ed script, your job is done in no time:

ed ~/.bashrc<<EOF
/^# aliases
+,/^# end aliases/-1d
-r !sed -n '/^# aliases/,/^# end aliases/p' stuff-to-place-in-bashrc.txt|grep -v '^#'
w
q
EOF

I use similar scripts to automatically tune configuration files, such als .asoundrc for different environments I take my laptop to.

The best document about ed comes as a simple manual page from the very cool PLAN9 system. I translated it to a ed.ps postscript document.
If you are interested in PLAN9 you should check 9front and http://cat-v.org/ as the original bell labs version is still maintained but has a very simple filesystem.

A final word about editor wars, emacs, vim and the like: acme rules!

Method 2

set /^#aliases/  /^#end aliases/
sed -ne"$1,$2"'s/\{0,1}/&&/gp' <stuff_to_place...rc |
sed -e"$1,$2c" -f- ./infile >./outfile

If you want to edit the file in-place ed is a very good solution. If you want to edit it in-stream, use sed. Avoid sed -i.

Method 3

Sure, you can do this with ed alone, no need for additional tools:

ed -s stuff_to_place.txt<<IN
1,/# aliases/d
/# end aliases/,$d
,d
.r /home/username/.bashrc
/# aliases/x
.t.
.,/# end aliases/-d
,p
q
IN

if you’re happy with the result, replace ,p with w /home/username/.bashrc to write the changes to ~/.bashrc (note the full path used with r and w; you can simply use .bashrc if it’s in cwd).
How this works: we first delete the unneeded lines from stuff_to_place.txt. Then we delete the remaining ones (the aliases) with ,d. The text buffer is now empty while the cut buffer contains the lines we want. We then read the content of .bashrc into the text buffer, put the content of the cut buffer (x) to after the /# aliases/ line, duplicate the last line that was pasted (.t.) then delete from the duplicated line up to but not including /# end aliases/ and finally print or write changes and quit.

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0