Making a New Command Version
[previous]
[next]
[table of contents] [index]
This section explains the steps you'll use to make a new MH command version.
Some of the steps need to be done only once before making the first new
command version.
For example, you can make a new version of the scan command
called tscan.
After this, if you type the command scan, it will work the way it
always has.
But if you use tscan, it will automatically use the
-form scan.timely switch to show the date in a different style,
as shown in the following example:
% scan 3-5
3 02/04*To:vicki@maxa.nap Problems with maxa<<Vicki, I thi
4 12/14 To:uunet!xyz!pamb Holiday Greetings<<Pam, I just w
5 04/06 mary@hahvahd.edu rcvtty -- how do I use it?<<I've
% tscan 3-5
3 Sun *To:vicki@maxa.nap Problems with maxa<<Vicki, I thi
4 14Dec To:uunet!xyz!pamb Holiday Greetings<<Pam, I just w
5 Apr92 mary@hahvahd.edu rcvtty -- how do I use it?<<I've
Let's start with a summary of the steps.
Do these steps only once before making the first version
(the Section
Setup Before You Make First New Version
explains how to do that):
-
Make a bin directory if you need one.
-
Choose the best way to make new versions on your host.
Do these steps for making each new version (see the Section
What to Do for Each New Version):
-
Pick a new name for the version.
Be sure it's not already in use.
-
Add an entry for the version to your MH profile.
-
Find the pathname of the MH command you're making a version of.
-
Make the version, the way it was chosen in the Section
Setup Before You Make First New Version.
-
If you use the C shell, run its rehash command.
The Chapter
Key Parts of the UNIX Filesystem
will help, too.
This section has overall setup that you'll only need to do once.
Making a bin Directory, Setting Search Path
You need a place to put your new MH programs.
This can be a directory on your account.
Or, if several people want to use these programs, you could pick any other
directory -- as long as you have write access to it.
Usually, the directory's name is something like bin.
Here are the steps:
-
If you haven't set up a directory for programs, make one.
For instance, to make a bin under your home directory, type:
% cd
% mkdir bin
-
If you have the directory for storing programs, be sure that the programs
in it are accessible.
Type the command echo $PATH and look for the directory's
pathname.
For instance, if your directory is called /u/walt/bin, you should see:
% echo $PATH
...:/u/walt/bin:...
If the directory isn't in your PATH, add it.
Do that by editing the PATH=... line in your .profile file
or the set path=(...) line in your .cshrc
or .login file.
Add the full pathname of the directory to the end of the PATH.
Then, for the Bourne and Korn shells, type the command:
$ . .profile
For the C shell, type one of these commands, depending on which file
you changed:
% source .cshrc
% source .login
Finally, if other people are sharing the directory, use a command like
chmod go+rx bin to give them access.
Finding the Best Way to Make New Versions
The first time you make a new command version, you'll need to figure out
how to do it on your particular account and computer.
There are a few different ways.
Here's how to decide which one is best for you:
-
If your version of UNIX has symbolic links, this is usually the
easiest way.
(If you aren't sure, type man ln and look for the
-s option.)
Some people call these soft links.
For example, to make the version of scan called tscan,
you first find where the scan program is stored.
(There are instructions for doing that below.)
Then, you cd to your bin directory and type commands like:
% ln -s /usr/local/mh/scan tscan
% ls -l tscan
lrwxrwxrwx 1 eds 16 Jul 1 14:32 tscan -> /usr/local/mh/scan
% ls -lL tscan
-rwxr-xr-x 1 root 81920 May 26 19:04 tscan
The ls -l command shows the link itself and the
ls -lL command shows the file that the link "points to."
There's one thing to watch out for:
each symbolic link takes a block of disk space.
If you're short on disk space and you plan to make a lot of symbolic
links, you may want to use one of the three other methods below.
-
If you won't be using symbolic links, you may be able to use standard
links (I'll call them hard links).
These are the same kind of links that MH makes between linked messages.
Hard links are good because they take virtually no filesystem space.
But they won't work if the programs you want to link to are on a
different filesystem.
(If you're not sure whether the program is on a different filesystem,
try to make the link and see if it works, or ask a local expert.)
Another problem with hard links can happen when the system administrator
installs a new version of the program you're linked to.
Unless the administrator is careful, you could end up with a link to
the old version of the program, instead of the new one!
(There's one workaround here:
the system administrator could make a system
directory and put the hard links there for everyone on the system to use.)
The bottom line:
if you want to make hard links, talk to your system administrator.
Here's how to make a hard link.
For example, to make the version of scan called tscan,
you'd first find where the scan program is stored.
Then, you'd cd to your bin directory and type commands like:
% ln /usr/local/mh/scan tscan
% ls -li /usr/local/mh/scan tscan
13256 -rwxr-xr-x 2 root 81920 May 26 19:04 /usr/local/mh/scan
13256 -rwxr-xr-x 2 root 81920 May 26 19:04 tscan
If you make hard links, it's a good idea to use ls -li every so
often, to compare the original program with your link.
If the two listings are different (except for the names), your link to
the system version was broken.
-
If symbolic links and hard links don't appeal to you, a small program called
execit,
written in the C language, might be what you want.
execit will run an MH command under any name you choose.
If your UNIX system has a C compiler (usually named cc or gcc),
that and the ln command are all you need to use execit.
To set up execit, edit a simple table of renamed commands in a
file called execit.include.
Then compile the execit.c file with one command.
Finally, run a shell script named execit.link to make the links
for you:
% vi execit.include
...Add a line for tscan to the table...
% cc -o execit execit.c
% execit.link
The execit.link script makes as many hard links to the execit
program as you need, one link per version.
If you're making many command versions, this can save disk space
as compared to symbolic links.
After you've done the first-time setup in the Section
Setup Before You Make First New Version
(which you only need to do once), you're ready for this section.
Here are the overall steps to do each time you make a new version of
an MH command:
-
Pick a new name for your MH version.
For instance, you might call it tscan.
Make sure that it doesn't conflict with any other commands on the
system by typing one of the commands in the following example.
If you get output (besides an error) from one of them, there's
probably already a command with the same name.
(The whence command works on the Korn shell; I've shown it
with the ksh dollar sign ($) prompt.)
% man 1 tscan
No manual entry for tscan in section 1.
% which tscan
no tscan in . /xxx/ehuser/bin /usr/bin/X11 /usr/local/bin ...
% whereis tscan
tscan:
$ whence tscan
-
Once you find an unused name, add an entry for the command to
your MH profile.
The entry starts with the name of your command, then has a colon,
and finally shows the command-line switches you want to use with the program.
For instance, the entry for tscan could be:
tscan: -form scan.timely
Be sure not to leave any blank lines in the file.
-
Find out where the actual MH command is located by typing each of the
following commands until you get an answer:
% which scan
% whereis scan
$ whence scan
The answer should be a pathname, something like /usr/local/mh/scan.
If you still can't find it, type ls in the MH binary directory or
ask an expert for help.
-
Make the symbolic link or hard link or use execit as explained in
the Section Setup Before You Make First New Version.
-
If you're using the C shell, type the following
command to reset the shell's command search table:
% rehash
That's it.
Try your new version.
If you want to change the switches you chose, you just need to edit
your MH profile.
If you get an error such as the following:
tscan: command not found
there's a problem with your shell's search path, your link, or your
execit.include file.
Reread these instructions carefully -- if that doesn't help, it's time
to get your guru.
Once you get the hang of these steps, it only takes a minute to add a
new command version.
|
