Bash: Inserting one file's content into another file after the pattern

Question

I\'m trying to write a bash script, which will do the following:

1. reads the content from the first file (as a first argument)
2. reads the content from th

Answer 1

Using awk works as well.

To insert before the ###marker### line :

// for each  of second_file.txt :
//   if  matches regexp ###marker###, outputs first_file.txt.
//   **without any condition :** print 
awk '/###marker###/ { system ( "cat first_file.txt" ) } \
     { print; } \' second_file.txt

To insert after the ###marker###line :

// for each  of second_file.txt :
//   **without any condition :** print 
//   if  matches regexp ###marker###, outputs first_file.txt.
awk '{ print; } \
     /###marker###/ { system ( "cat first_file.txt" ) } \' second_file.txt

To replace the ###marker### line :

// for each  of second_file.txt :
//   if  matches regexp ###marker###, outputs first_file.txt.
//   **else**, print 
awk '/###marker###/ { system ( "cat first_file.txt" ) } \
     !/###marker###/ { print; }' second_file.txt

If you want to do in-place replacement, use a temp file for being sure the pipe doesn't start before awk has read the entire file; add :

> second_file.txt.new
mv second_file.txt{.new,}
// (like "mv second_file.txt.new second_file.txt", but shorter to type !)

If you want replacement inside of the line, (replacing just the pattern and keeping the rest of the line), a similar solution should be achievable with sed instead of awk.