Fig. 1
Unix commands may seem
a little cryptic at times.
Basic Unix Commands are a topic of another small HowTo. For now we look
at just a few possible problem areas. The command ls -la
which was used at the beginning of this HowTo, and shown again here in
Fig. 1, is
a case in point.
There must be a space
between the command ls and the
argument -la. Without the space ls-la would be
interpreted as a one word command. The response would be: ls-la: command not found.
If your home directory is even slightly extensive, the ls -la command
will cause the files in your home directory to scroll by to the end of
the list,
not giving you a chance to see what they are. This is rectified
with: ls -la |
more. This will cause one screenfull of files to display at a
time. A spacebar
displays the next screenfull. A return will
display the next line.
For the same reason as
cited above, the command vi .exrc needs a
space between vi
(the command) and the filename .exrc (the
argument). Additional arguments may be given as well. For example,
entering vi +215
.exrc will start editing the .exrc file at
line #215, which would indicate a really big .exrc file. For
other files however, this can be useful.
For Windoze users, it
may seem odd that it would matter that the vi command can't
be entered as VI.
Well, it can't. Upper and lower case are significant just about
everywhere in Unix.
In the "long list" in
Fig. 1, the "." all the way to
the right of the first line means "current directory". In order to
successfully edit and save a file in this directory, you must have
"write permission". At the left end of this line is the mysterious drwxr-xr-x. The
"d" means it is a directory, and then there follows three combinations
of "rwx"
meaning Read,
Write, eXecute. The
first 3 are the permissions of the "user" (dork in this
case), the second 3 are permissions of the "group" (mech in this
case), and the third 3 are for the rest of the world. As can be seen in
the example, Dork has read, write and execute permissions for this
directory (/home/dork). While read & write have fairly obvious
meanings, execute, in the context of a directory may be confusing. At
the top of Fig. 1, the command cd /home/dork
was entered. Without execute permission for this directory, the
response to that command would have been "permission denied".
That would mean that you are excluded from the /home/dork
directory. Maybe you've been bad. The group mech and the
rest of the world can enter this directory and read the list of files
contained in
it, but are not allowed to
create or modify files in it.
Part
3 will deal with some commands available in vi.