Add info under specific line

Question

I want to know how could I add files contain information under specific line in file.

For example, I have file1.txt with the following lines:

line 1
line 2
line 3

and file2.txt has the information I want to add in file1.txt under specific in line 2.

How could this to be done?

Answer 1

Use Sed's R[ead] Command

You can use sed's r command to read in a file. For example, to match the line by its number:

sed '2 r /tmp/file2.txt' /tmp/file1.txt

Or if you prefer to match the line by its content:

sed '/^line 2/ r /tmp/file2.txt' /tmp/file1.txt

This is a standard command, and doesn't rely on any GNU extensions, so it should work across different sed implementations.

The commands above print the result on their standard output. If you want to modify the original file, add the -i option just after sed (this will work on Linux and Cygwin but not on all unix systems).

Answer 2

Besides sed you can also do this with awk:

awk '1; /line 2/ { while(getline < "file2.txt") print }' file1.txt

This will insert the contents of file2.txt every time line 2 is encountered.

The 1 is the default block { print $0 }.

This sends its output to standard output, if you want to overwrite file1.txt save the output to a temporary file and overwrite:

awk '1; /line 2/ { while(getline < "file2.txt") print }' file1.txt > file1.txt.tmp
mv file1.txt.tmp file1.txt

Edit

For fixed string matching == would be more reliable, e.g. to match the mentioned string use this conditional:

awk '1; $0 == "\"zend_extension=/usr/local/Zend/lib/Optimizer-3.3.9/php-5.2.x/ZendOptimizer.so\"" { while(getline < "file2.txt") print }' file1.txt

Note this needs to match the whole line.