Dr. Mark Humphrys

School of Computing. Dublin City University.

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Online coding site: Ancient Brain

coders   JavaScript worlds


CA170      CA2106      CA686      CA686I

Online AI coding exercises

Project ideas

Introduction to UNIX / Linux (More)

Some Commands to get started

Explore commands and options by typing "man (command)"
e.g. "man ps"

clear                   Clear screen


ls                      List files
ls -a                   Show "hidden" files (begin with ".")
ls -l                   Detailed
ls -alR                 Recursive

cat (file)              Type file out in command-line window

more (file)             Type file, pause for each screenful
                        enter for new line, space for next page, q to quit

Manipulating files

Human can use GUI file manager. Programs can do anything a human can do, with these commands. Human sometimes types these commands too.

cp                      Copy files
mv                      Move / Rename files
rm                      Remove files
mkdir                   Make directory
rmdir                   Remove directory
See tutorials on manipulating files with cp, mv, rm, etc.

Detach program (&)

(prog) &                Launch a process detached 
                         from command-line (e.g. windowed)
(prog)                  Command-line frozen until prog exits.

eog file.jpg &		Launch image viewer Eye of GNOME on file

Web browsers

firefox &              Launch Web browser from command-line
firefox "URL" &
google-chrome &

konqueror "URL" & 


sort 		Sort alphabetically (pipe some stream into sort)
sort -n		Sort numerically
sort -r		Reverse sort 

sort by 5th column:
sort -k 5

old syntax to sort 5th column:
sort +4     



grep      Search for a string in a file or files

grep (string) (file)
grep (string) *html 

grep -i (string) (file)  Ignore case
grep -v (string) (file)  Return lines that do NOT match 


find      Find files by type/date/name, in this dir or below 

find -type d       Find all dirs 
find -mtime -1     Find files modified today


lp (file)               Print
lpr (file)              Print (on some systems)
lp -Pl128 (file)        Print on printer l128 (L128)

lpq                     See print queue
lprm                    Remove job from queue


cal                     Calendar

cal 8 1752              Calendar for Aug 1752
cal 9 1752              Calendar for Sept 1752
cal 10 1752             Calendar for Oct 1752



which (prog)            
 what runs if "prog" is typed
 may return nothing if prog is an alias

which ls

type (prog)
 returns path of prog
 or else shows what prog is alias for

type h
type history

whereis (prog)		Where the binary, source, manual pages are for this prog
whereis perl


w                       Who is logged in
           (see this when you ssh student.computing.dcu.ie)
(command) ; (command)   Multiple commands on same line


Command-line HTTP client.

wget -q -O - URL      					  	Download URL, quiet, output to command-line
wget -q -O - URL > file.htm 					Output to file

wget -q -O file.htm  URL  					Output to file

wget -q -O - http://site/file.jpg  > file.jpg 		Output JPEG to file (output JPEG to command-line won't work)

wget -q -O file.jpg  http://site/file.jpg   		Output JPEG to file 

 see more on wget

wget appears in this hacking scene from the movie The Social Network (2010).
Perhaps the most realistic hacking scene in the history of movies.

ancientbrain.com      w2mind.org      humphrysfamilytree.com

On the Internet since 1987.

Note: Links on this site to user-generated content like Wikipedia are highlighted in red as possibly unreliable. My view is that such links are highly useful but flawed.