Inserting text from a file at the beginning of another file - bash

Question

I am trying to insert some copy information at the beginning of some source files. I know using sed as follows:

sed "1iSome copyrighted information." sample.txt 

will insert the text “Some copyrighted information” at the beginning of sample.txt.
I need to insert text from a file at the beginning of sample.txt. Is there any way in sed that I could use the cat for the specified purpose, say something like this:

 sed "1i{cat header.txt}" sample.txt 

I have googled for the above and did not find exactly what I was looking for. Any help on this is welcome.

Thanks.

Answer 1

Use the ed text editor:

 echo -e '0r header.txt\nw' | ed sample.txt 

or use the vi / ex command:

 vi - +'0r header.txt|wq' sample.txt 

But I do not see the ability to run the command in sed.

Answer 2

If you have GNU sed :

 sed -i -e '2{x;G};1{h;rheader.txt' -e 'd}' sample.txt 

sample.txt must contain at least two lines.

This method works even if the header file contains characters special to sed .

Explanation:

• -i - edit the file in place
• -e - partition the script - this is necessary in this case to delimit the end of the header file name (it can also be separated by a newline)
• 1{h; - in the first line of the file (sample.txt) save it to store a space
• rheader.txt - read in the header file (header.txt)
• d} - delete the initial first line of the file from the template space and finish processing line 1 - deleting it here prevents the insertion of an additional empty line at the beginning of the file
• header file content is now displayed
• 2{x; - when reading line 2 of the file (sample.txt), change it to hold and replace the free space (containing the original line 1) with the drawing space
• G} - add a hold space to the end of the pattern space (which now contains the source lines 1 and 2) and finish processing line 2
• lines 1 and 2 are now output, then processing continues for the rest of the file, which consists in simple reading and output of each line.

Edit: I removed the extra command from the originally published version.

Answer 3

Sorry to use the whole answer - just for the sake of formatting :) Basically, the same answer from @tangens, but without a temporary file:

 echo "$(cat header.txt sample.txt)" > sample.txt 

Pay attention to the quotation marks ( " ) to preserve the end of the line, and the fact that cat is concatenated in the subprocess - so it should not be possible to overwrite the file ( sample.txt ) that is open for reading.

Hooray!

Answer 4

 cat header.txt sample.txt > temp.txt mv temp.txt sample.txt 

Answer 5

If you really want to do this using sed :

 INFO=$(cat header.txt) # read the contents of file headers.txt into var INFO sed -i "1i$INFO" sample.txt # insert $INFO, use -i to change the file inplace 

However, I would use the cat method.

Answer 6

Why not do it the other way around, for example. add source files to your copyright file?

The 'cat' command is actually short for 'concatenate', you can just say

 for f in *.c do cp $f /tmp cat copyright.txt /tmp/$f >$f done