Assignment #3

Unix Command Summary
See the Unix tutorial for a leisurely, self-paced introduction on how to use the commands listed below. For more documentation on a command, consult a good book, or use the man pages. For example, for more information on grep, use the command man grep.
Contents
cat --- for creating and displaying short files
chmod --- change permissions
cd --- change directory
cp --- for copying files
date --- display date
echo --- echo argument
ftp --- connect to a remote machine to download or upload files
grep --- search file
head --- display first part of file
ls --- see what files you have
lpr --- standard print command (see also print )
more --- use to read files
mkdir --- create directory
mv --- for moving and renaming files
ncftp --- especially good for downloading files via anonymous ftp.
print --- custom print command (see also lpr )
pwd --- find out what directory you are in
rm --- remove a file
rmdir --- remove directory
rsh --- remote shell
setenv --- set an environment variable
sort --- sort file
tail --- display last part of file
tar --- create an archive, add or extract files
telnet --- log in to another machine
wc --- count characters, words, lines

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.
Files
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.
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
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.
File Compression
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
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.
Finding things
ff --- 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. In fact, if you use ff -p you don't even need the full name, just the beginning. This can also be useful for finding other things on the system, e.g. documentation.
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 to you.
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 the moment.
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 location.
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.
talk username --- lets you have a (typed) conversation with another user
write username --- lets you exchange one-line messages with another user
elm --- lets you send e-mail messages to people around the world (and, of course, read them). It's not the only mailer you can use, but the one we recommend. See the elm page, and find out about the departmental mailing lists (which you can also find in /user/linguistics/helpfile).
Miscellaneous tools
webster word --- looks up the word in an electronic version of Webster's dictionary and returns the definition(s)
date --- shows the current date and time.
cal --- shows a calendar of the current month. Use e.g., 'cal 10 1995' to get that for October 95, or 'cal 1995' to get the whole year.