The instructions are at
Vijay Adusumalli will be in the CS majors lab in the basement of the Love Building from 11:00am until 1:00pm everyday from Wednesday, January 23, until Monday, January 28, (except for Sunday, January 27) to help you if you cannot get set up.
Fundamental to the idea of Unix is the idea of "logging in". This means
ls is a useful command; like dir in the Windows world, it shows you what is in a directory.
The most useful options are
On the "root", you expect to find at least these directories:
In addition, you are likely to also see at least these:
We do have standards:
In addition to any files and directories that you might create in your home directory, there are often a number of other files and directories that might be there.
Generally these are what we call "dot" files: literally, the first character in the file/directory name is a period.
The program ls ignores such files unless it has been given the -a (all) option.
In addition, what we call "globbing" ignores "dot" files unless you explicitly include such a dot.
So what is "globbing"? The idea behind globbing is to treat the characters "*", "?", "[]", "{}", and "~" as "metacharacters".
"Dot" files generally are used by programs such as shells and windowing environments which have a need to have and retain complex state, such as startup commands and current information.
the major ways:
To change permissions, we use the chmod command:
chmod u+x # add execute permission for the user chmod g+x # add execute permission for group chmod o+x # add execute permission for other chmod a+x # add execute permission for all users chmod a-x # remove execute permission for all users chmod g-r # remove read permission for group
Shells generally have an "built-in" command called umask which allows the user to specify the default permissions for newly created files.
It actually specifies the complement of the default read-write permissions for newly created files.
umask 077 # no one except the user can read or write new files umask 000 # anyone can read or write all new files (dangerous!) umask 022 # anyone can read but not write new files umask 777 # no one (not even the owner) can read or write new files
% cal 1776 > 1776.calendar.txt % cal 1752 > 1752.calendar.txt
We can use many programs to examine this file: cat, less, and od are among the most popular, but also head, tail, and even grep are also quite useful.
You can use cat to join multiple files together:
cat 1776.calendar.txt 1752.calendar.txt > both.txt
cat 17{76,52}.calendar.txt > both.txt
# or with append
cat 1776.calendar.txt > both.txt
cat 1752.calendar.txt >> both.txt
cp both.txt copy.txt # copies, but uses new date and
# umask default permissions for new file
cp -a both.txt # creates an exact copy
cp -r .mozilla .mozilla-backup # creates a new copy of a dir
# but times are new and permissions
# are umask-controlled
cp -a .mozilla .mozilla-exact # creates an exact copy of a dir
Moving files with mv is usually far faster than copying the same files with cp. If a file is in the same filesystem (and if it's in your home directory it very likely is), then mv just changes some directory information rather than doing anything with the contents. cp of course must work with the contents (unless you are using a very sophisticated filesystem that understands on-the-fly deduplication.)
mv both.txt old.txt
mv .mozilla .mozilla-2013-01-22 # notice that no option is necessary
# to specify directory operations
Removing files is easy — maybe too easy!
rm old.txt rm -rf .mozilla # remove a directory without complaining rm -rf / # remove everything in the system (bad idea!) rmdir .somedir/ # doesn't work unless .somedir/ is empty