In general arguments to commands have a -, but - by its self means something completely different.

ls - show the names of the files in this directory.

-a - show all files,


[bennett@douc54 two]$ /bin/ls  
.               a.out           foo.C    goals.html  id.gif   structure.html
..              constants.html  foo.cpp  ident.html  one.cpp  variables.html

-l - long listing


[bennett@douc54 two]$ /bin/ls -l
total 64
-rwxrwxr-x    1 bennett  bennett     14414 Sep 11 11:26 a.out
-rw-rw-r--    1 root     root          104 Sep 14 11:11 constants.html
-rw-rw-r--    1 bennett  bennett        25 Sep 14 11:26 foo.C
-rw-rw-r--    1 bennett  bennett        91 Sep 11 11:25 foo.cpp
-rw-rw-r--    1 bennett  bennett       868 Sep 10 13:29 foo.dvi
-rw-rw-r--    1 bennett  bennett       727 Sep 10 13:29 foo.tex
-rw-rw-r--    1 bennett  bennett       956 Sep 10 11:34 goals.html
-rw-rw-r--    1 bennett  bennett      1413 Sep 10 13:41 ident.html
-rw-rw-r--    1 bennett  bennett      3500 Sep 10 13:32 id.gif
-rw-rw-r--    1 bennett  bennett       349 Sep 10 13:12 one.cpp
-rw-rw-r--    1 bennett  bennett      1844 Sep 10 13:54 structure.html
-rw-rw-r--    1 root     root         7001 Sep 14 11:40 variables.html

cp - copy from one file to another

cp oldfile newfile
VERY CAREFUL, it doesn't ask

mv - move from one file to another

mv oldfile newfile
VERY CAREFUL, it doesn't ask

rm - remove a file

rm filename
VERY CAREFUL, it doesn't ask