Basic UNIX commands
Note: not all of these are actually part of UNIX itself, and you may
not find them on all UNIX machines. But they can all be used on turing
in essentially the same way, by typing the command and hitting
return. Note that some of these commands are different on non-Solaris
machines - see SunOS differences.
If you've made a typo, the easiest thing to do is hit CTRL-u to
cancel the whole line. But you can also edit the command line (see the
guide to More UNIX).
UNIX is case-sensitive.
- ls --- lists your files
ls -l --- lists your files in 'long format', which contains lots of
useful information, e.g. the exact size of the file, who owns the file
and who has the right to look at it, and when it was last modified.
ls -a --- lists all files, including the ones whose filenames begin in
a dot, which you do not always want to see.
There are many more options, for example to list files by size, by
date, recursively etc.
- more filename --- shows the first part of a file,
just as much as will fit on one screen. Just hit the space bar to see
more or q to quit. You can use /pattern to
search for a pattern.
- emacs filename --- is an editor that lets you
create and edit a file. See the emacs page.
- joe filename --- simple editor. Press ctrl+K followed by H for help, ctrl+C abort, ctrl+K followed by X for save and exit
- mv filename1 filename2 --- moves a file (i.e. gives
it a different name, or moves it into a different directory (see below)
- cp filename1 filename2 --- copies a file
- rm filename --- removes a file. It is wise to use
the option rm -i, which will ask you for confirmation before actually
deleting anything. You can make this your default by making an alias in your .cshrc file.
- diff filename1 filename2 --- compares files, and
shows where they differ
- wc filename --- tells you how many lines, words,
and characters there are in a file
- tr set1 set2 --- transfer characters from set1 to set2. Example tr [a-z] [A-Z] converts small characters to big ones.
- chmod options filename --- lets you change the read,
write, and execute permissions on your files. The default is that only
you can look at them and change them, but you may sometimes want to
change these permissions. For example, chmod o+r
filename will make the file readable for everyone, and
chmod o-r filename will make it unreadable for others
again. Note that for someone to be able to actually look at the file
the directories it is in need to be at least executable. See help protection for more details.
- sed --- stream editor. Automatically modifying files. For more information see Sed
- File Compression
- tar -czf archiv_name list_of_files - compresses files into tar gziped format. Standard extension for such a compress files is .tgz.
- tar -xzf archiv_name where - extract files from archiv to selected destination. See man tar for more options.
- gzip filename --- compresses files, so that they
take up much less space. Usually text files compress to about half
their original size, but it depends very much on the size of the file
and the nature of the contents. There are other tools for this
purpose, too (e.g. compress), but gzip usually gives the
highest compression rate. Gzip produces files with the ending '.gz'
appended to the original filename.
- gunzip filename --- uncompresses files compressed by gzip.
- gzcat filename --- lets you look at a gzipped file without
actually having to gunzip it (same as gunzip -c). You can even
print it directly, using gzcat filename | lpr
Directories, like folders on a Macintosh, are used to group files
together in a hierarchical structure.
- mkdir dirname --- make a new directory
- cd dirname --- change directory. You basically 'go'
to another directory, and you will see the files in that directory
when you do 'ls'. You always start out in your 'home directory', and
you can get back there by typing 'cd' without arguments. 'cd ..' will
get you one level up from your current position. You don't have to
walk along step by step - you can make big leaps or avoid walking
around by specifying pathnames.
- pwd --- tells you where you currently are.
- find --- find files anywhere on the system. This can be
extremely useful if you've forgotten in which directory you put a
file, but do remember the name.
- grep string filename(s) --- looks for the string in
the files. This can be useful a lot of purposes, e.g. finding
the right file among many, figuring out which is the right version of
something, and even doing serious corpus work. grep comes in several
varieties (grep, egrep, and fgrep) and has a lot
of very flexible options. Check out the man pages if this sounds good
About other people
- w --- tells you who's logged in, and what they're doing.
Especially useful: the 'idle' part. This allows you to see whether
they're actually sitting there typing away at their keyboards right at
- who --- tells you who's logged on, and where they're
coming from. Useful if you're looking for someone who's actually
physically in the same building as you, or in some other particular
- finger username --- gives you lots of information
about that user, e.g. when they last read their mail and whether they're
logged in. Often people put other practical information, such as phone
numbers and addresses, in a file called .plan. This information is
also displayed by 'finger'.
- last -1 username --- tells you when the user last
logged on and off and from where. Without any options, last will
give you a list of everyone's logins.
- write username --- lets you exchange one-line
messages with another user
About your (electronic) self
You can find out more about these commands by looking up their
- whoami --- returns your username. Sounds useless, but
isn't. You may need to find out who it is who forgot to log
out somewhere, and make sure *you* have logged out.
- finger & .plan files
of course you can finger yourself, too. That can be useful e.g.
as a quick check whether you got new mail. Try to create a useful
.plan file soon. Look at other people's .plan files for ideas. The
file needs to be readable for everyone in order to be visible through
'finger'. Do 'chmod a+r .plan' if necessary. You should realize that
this information is accessible from anywhere in the world, not just to
other people on turing.
- passwd --- lets you change your password, which you should
do regularly (at least once a year). See the LRB guide and/or look at help password.
- ps -u yourusername --- lists your processes. Contains lots of
information about them, including the process ID, which you need
if you have to kill a process. Normally, when you have been kicked out
of a dialin session or have otherwise managed to get yourself
disconnected abruptly, this list will contain the processes you need
to kill. Those may include the shell (tcsh or whatever you're using),
and anything you were running, for example emacs or elm. Be careful
not to kill your current shell - the one with the number closer to
the one of the ps command you're currently running. But if it happens,
don't panic. Just try again :) If you're using an X-display you may
have to kill some X processes before you can start them again. These
will show only when you use ps -efl, because they're root
- kill PID --- kills (ends) the processes with the ID
you gave. This works only for your own processes, of course. Get the
ID by using ps. If the process doesn't 'die' properly, use
the option -9. But attempt without that option first, because it
doesn't give the process a chance to finish possibly important
business before dying. You may need to kill processes for example if
your modem connection was interrupted and you didn't get logged out
properly, which sometimes happens.
- quota -v --- show what your disk quota
is (i.e. how much space you have to store files), how much you're
actually using, and in case you've exceeded your quota (which you'll
be given an automatic warning about by the system) how much time you
have left to sort them out (by deleting or gzipping some, or moving
them to your own computer).
- du filename --- shows the disk usage of the files and
directories in filename (without argument the current directory
is used). du -s gives only a total.
- last yourusername --- lists your last logins. Can
be a useful memory aid for when you were where, how long you've been
working for, and keeping track of your phonebill if you're making a
non-local phonecall for dialling in.
man commandname --- shows you the manual page for
For further ways of obtaining help, look at the pages with electronic sources of information
and non-electronic sources.