Linux Advanced Text Processing Tools

script
Log my current session in the text terminal into text file typescript . The log finishes when I type exit or press d.

emacs
(in X-terminal) The emacs text editor. Advanced and sophisticated text editor. Seems for gurus only: "emacs is not just an editor, it is a way of living". Emacs surely seems rich or bloated, depending on your point of view. There are likely 3 versions of emacs installed on your system: (1) text-only: type emacs in a text (not X-windows) terminal (I avoid this like fire); (2) graphical-mode: type emacs in an X-windows terminal (fairly usable even for a newbie if you decide to take some time to learn it); and (3) X-windows mode: type "xemacs" in an X-windows terminal.

vi
The famous (notorious?) "vi" text editor (definitely not recommended for newbies). To exit "vi" (no changes saved) use these five characters: :q! I use the pico text editor and don't ever need vi (well, unless I have to unmount the /usr subsystem and modify/edit some configuration files, then vi is the only editor avialable). To be fair, modern Linux distributions use vim (="vi improved") in place of vi, and vim is somewhat better than the original vi used to be. The GUI version of vi is also available (type gvim in an X terminal).

Experts do love vi, but vi is definitely difficult unless you use it every day. Here is a non-newbie opinion on vi (http://linuxtoday.com/stories/16620.html):

"I was first introduced to vi in 1988 and I hated it. I was a freshman in college... VI seemed archaic, complicated and unforgiving... It is now 12 years later and I love vi, in fact it is almost the only editor I use. Why the change? I actually learned to use vi... Now I see vi for what it really is, a powerful, full featured, and flexible editor..."

A short introduction to basic vi commands and modes can be viewed at http://www.thelinuxgurus.org/vitut.shtml.

For your entertainment, you may also want to try the even more ancient ed editor (just type ed on the command line).

nano
This is a brand new (March 2001) GNU replacement for pico. Works and looks like pico, but it is smaller, better, and licenced as expected for a decent Linux piece of software (i.e., GPL). Not yet included with RH7.0 or MDK7.2, but expect it soon to be.

khexedit
(in X terminal) Simple hexadecimal editor. Another hexadecimal editor is hexedit (text based, less user=friendly). Hex editors are used for editing binary (non-ASCII) files.

diff file1 file2 > patchfile
Compare contents of two files and list any differences. Save the output to the file patchfile.

sdiff file1 file2
Side-by-side comparison of two text files. Output goes to the "standard output" which normally is the screen.

patch file_to_patch patchfile
Apply the patch (a file produced by diff, which lists differences between two files) called patchfile to the file file_to_patch. If the patch was created using the previous command, I would use: patch file1 patchfile to change file1 to file2.

grep filter
Search content of text files for matching patterns. Definitely worth to learn at least the basics of this command.

A simple example. The command:

cat * | grep my_word | more

will search all the files in the current working directory (except files starting with a dot) and print the lines which contain the string "my_word".

A shorter form to achieve the same may be:

grep my_word * |more

The patterns are specified using a powerful and standard notation called "regular expressions".

There is also a "recursive" version of grep called rgrep. This will search all the files in the current directory and all its subdirectories for my_word and print the names of the files and the matching line:

rgrep -r my_word . | more