Add text between two patterns in File using sed command

Question

I want to add Some large code between two patterns:

File1.txt

This is text to be inserted into the File.

infile.txt

Some Text here
First
Second
Some Text here

I want to add File1.txt content between First and Second :

Desired Output:

Some Text here
First
This is text to be inserted into the File.
Second
Some Text here

I can search using two patterns with sed command ,But I don't have idea how do I add content between them.

sed '/First/,/Second/!d' infile 

Answer 1

Since /r stands for reading in a file, use:

sed '/First/r file1.txt' infile.txt

You can find some info here: Reading in a file with the 'r' command.

Add -i (that is, sed -i '/First/r file1.txt' infile.txt) for in-place edition.

To perform this action no matter the case of the characters, use the I mark as suggested in Use sed with ignore case while adding text before some pattern:

sed 's/first/last/Ig' file

---

As indicated in comments, the above solution is just printing a given string after a pattern, without taking into consideration the second pattern.

To do so, I'd go for an awk with a flag:

awk -v data="$(<patt_file)" '/First/ {f=1} /Second/ && f {print data; f=0}1' file

Given these files:

$ cat patt_file
This is text to be inserted
$ cat file
Some Text here
First
First
Second
Some Text here
First
Bar

Let's run the command:

$ awk -v data="$(<patt_file)" '/First/ {f=1} /Second/ && f {print data; f=0}1' file
Some Text here
First                             # <--- no line appended here
First
This is text to be inserted       # <--- line appended here
Second
Some Text here
First                             # <--- no line appended here
Bar