Say I have a text file like this:
# custom content section
a
b
### BEGIN GENERATED CONTENT
c
d
### END GENERATED CONTENT
I'd like to replace the portion between the GENERATED CONTENT tags with the contents of another file.
What's the simplest way to do this?
lead='^### BEGIN GENERATED CONTENT$'
tail='^### END GENERATED CONTENT$'
sed -e "/$lead/,/$tail/{ /$lead/{p; r insert_file
}; /$tail/p; d }" existing_file
r insert_file command must be the last thing on its line. Note that neither whitespace nor comments are allowed after it. The code was tested using GNU sed with the --posix option enabled, and it worked as expected, so it should work with any posix compliant sed.
output=$(sed -e "..." existing_file)) and then perform the replacement in a second pass (e.g. echo "$output" > existing_file) since trying to redirect into a file you're reading from will cause it to truncate before contents are read.
Commented
Aug 2, 2016 at 12:44
newContent=`cat new_file`
perl -0777 -i -pe "s/(### BEGIN GENERATED CONTENT\\n).*(\\n### END GENERATED CONTENT)/\$1$newContent\$2/s" existing_file
Using a heredoc and the ed line editor:
ed -s FILE1 <<EOF
/### BEGIN GENERATED/+,/### END GENERATED/-d
/### BEGIN GENERATED/ r FILE2
w
q
EOF
The first line inside the heredoc is to delete (d) the line after (+) the ### BEGIN GENERATED and the line before (-) the ### END GENERATED...
The second line is to insert FILE2 after the line ### BEGIN GENERATED.
r FILE2 you can say r !command to read from a different script.
Warning: This is definitely not the simplest way to do it. (EDIT: bash works; POSIX grep is fine too)
If the main text is in file "main" and the generated content is in file "gen", you could do the following:
#!/bin/bash
BEGIN_GEN=$(cat main | grep -n '### BEGIN GENERATED CONTENT' | sed 's/\(.*\):.*/\1/g')
END_GEN=$(cat main | grep -n '### END GENERATED CONTENT' | sed 's/\(.*\):.*/\1/g')
cat <(head -n $(expr $BEGIN_GEN - 1) main) gen <(tail -n +$(expr $END_GEN + 1) main) >temp
mv temp main
Here is a Bash script using ed line editor to replace / update a part of multiline text in a text file with automatically generated content (eg: Table of contents) 👇
replace.sh
#!/usr/bin/env bash
# -*- coding: UTF-8 -*-
#
# github : https://github.com/JV-conseil
# www : https://www.jv-conseil.net
# author : JV-conseil
#===============================================
_lines=""
for i in {1..10}; do
_lines+=$'\n'"${i}. ""$(openssl rand -hex 12)"
done
ed -s "./sample.md" <<EOF
/## BEGIN GENERATED/+,/## END GENERATED/-d
/## BEGIN GENERATED/a
${_lines}
.
wq
EOF
sample.md
# How to replace part of a text file between markers with another text file?
Here is a Bash script using [ed line editor](https://www.gnu.org/software/ed/manual/ed_manual.html "GNU manual for ed line editor") to replace / update a part of multiline text in a text file with
automatically generated content (eg: Table of contents) 👇
## BEGIN GENERATED
1. d5c10e45943b196b005771f1
2. bc56de530fbf5342d55203b4
3. 9608f31a09c2ece9c9cee4dd
4. 54e361257aecce0a937211c0
5. c4b2edf88293df0747694c37
6. a80275accc9b2bc72d55efcd
7. 3a2e2fec5da23b415569de00
8. 524655319a05e7dd1f48e6a5
9. 879d17e9e611d163e5a85b02
10. 80d311a786efcd9d01da86f6
## END GENERATED
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Mauris et libero eu nunc
dapibus volutpat. Proin eu neque eu orci volutpat bibendum...
