you can use the unix cat command for this. here are some examples of usage:
cat file1 file2 file3 >bigfile (concatenates a list of files into one file) cat *.txt >bigfile.txt (same but using wildcarding to list the files) cat file.txt >>existingfile.txt (concatenating a file to the end of an existing file)
The stuff you can do from the command line in linux is crazy. The difficult part is knowing the commands :).
Doing search and replace/text finding type of things are crazy easy.
I'm no expert but I routinely use the two following: grep -R string * which looks recursively for 'string' in every file, down into the directory structure. Looking for a bit of code? just type that at the top of the directory and it'll find it for you.
The other one I use is a search and replace: perl -p -i -e 's/stringa/stringb/g' * which replaces all occurrences of stringa with stringb. (I think this is called the perl 'pie' or something like that).