Ttgjyuk

use

 grep -nr <your text> .

put the text that you want to find inside the <your text>

you can use

find . -name '*.*' -exec grep -Hn 'text to find' '' ;

-name '*.*' or '*.txt' (use file mask here)

'text to find' (place text you want to find here)

find . -type f -exec grep -Hn 'text to find' '' ;

if you want to search all files

GUI (Graphical) tool:

gnome-search-tool

you can find it in Ubuntu main menu

Menu -> Accessories -> Search for Files

or run it using hot key ALT+F2

I am a fan of searchmonkey (GPL, free, cross-platform, pretty light on resources and very fast).

Regexxer will let you search text in files. Not sure what you mean by "in folders".

Graphical search:

in Kubuntu open Dolphin, then Edit->Find (Ctrl+F)

change from filename to Content and adjust from where to look for.

Recoll does indexing and you can do full text searches of documents and email.

I compared three of the suggestions in here with 64 bit 16.04 Kubuntu:

1. Searchmonkey works with 64-bit Ubuntu nowadays. It is similar to
   regexxer. It appeared fast, but naturally it is much slower than
   index based search.


2. Search for Files and Alt-F2 don't work with
   the KDE Ubuntu version.


3. 
   

   My recommendation is Recoll and I have added some installation
   instructions for it. For me, the default installation supported PDF (test this!), DOCX, TAR, ZIP etc.

   
   
   

   sudo add-apt-repository "deb http://archive.canonical.com/ $(lsb_release -sc) partner"
   sudo apt-get install recoll antiword
   recoll
   

   
   



4. First line is probably not required: it adds partner installation repository.



5. Antiword is optional. It is needed to support older .doc files.


6. Enable following symbolic links and the root directory from Recoll Preferencies if necessary.


7. Create cron job for Recoll indexing using the GUI or make it to start on every login.


8. Change the Recoll setting in preferences from English to All languages if appropriate for you.


9. Start the indexing, at least for me it was surprisingly fast and didn't use all resources so I was able to continue using the laptop.


10. I have found one bug from Recoll so far: if you search for file name with "PST", it doesn't find it even though it is in uppercase. "pst" works and it finds both uppercase and lowercase names.


11. See more about recoll from https://www.lesbonscomptes.com/recoll/features.html

If you wish to add support for Outlook PST files, then you need to execute the following as well.

 sudo apt-get install readpst
 mkdir ~/PST
 find -L ~ -name "*.pst" -print | awk " printf "%s%s %s%s%s %s\n", "mkdir ~/PST/", $1, "; readpst -o ~/PST/", $1, " -D -j 4 -r -tea -u -w", $1 " > /tmp/myPstFiles
 cat /tmp/myPstFiles
 chmod 755 /tmp/myPstFiles
 /tmp/myPstFiles

1. Change root directory from ~ to / if necessary in the find command.


2. My find script has a bug in it: it creates too long directory structure now. But it was easier for me to modify the temp file manually than to find a fix to this. Main target was that this will work for several PST files and it does that.


3. See more about Readpst from http://www.five-ten-sg.com/libpst/rn01re01.html and https://blog.robseder.com/2015/08/29/working-with-a-pst-file-in-linux/
   

I'm really want to introduce one tool which is based on ncurses library to provide the text-based user interface. The tool called NCGREP(grep based on ncurses) is mainly for search text in the specific folder. Hope this is what you want.
This source of the tool has been hosted on github.com, see more at https://github.com/ncgrep/ncgrep

^{Click image to see demo animation}