symbolic links, aliases, cls clear

[mp]

i have a python program which attempts to call 'cls' but fails:

sh: line 1: cls: command not found

i tried creating an alias from cls to clear in .profile, .cshrc, and
/etc/profile, but none of these options seem to work.

my conclusion is that a python program that is executing does not use
the shell (because it does not recognize shell aliases). is this
correct?

should i use a symbolic link? if so, where should i place it?

what is the difference between aliases and symbolic links?

if i execute a command like 'clear' to clear the screen, where does the
shell look to find the command 'clear'?

i'm using os x.

thanks
mp

[Keith Thompson]

fl***@apaflo.co m (Floyd L. Davidson) writes:

af******@gmail. com wrote:

If I may recommend an alternative,

print "\033[H\033[J"

the ansi sequence to clear the screen.

Or so you would hope (however, that is *not* what you have listed!).

Unfortunately, it is poor practice to hard code such sequences.
Instead the proper sequence should be obtained from the
appropriate database (TERMINFO or TERMCAP), and the easy way to
do that is,

tput clear

(Or "clear".)

On the other hand, I think it's been at least a decade since I've used
a terminal or emulator that's not VT100-compatible (i.e., accepts ANSI
control sequences).

Of course, I'll run into one the day after I start writing code that
depends on that assumption.

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Chris F.A. Johnson]

On 2006-04-12, Floyd L. Davidson wrote:

af******@gmail. com wrote:

If I may recommend an alternative,

print "\033[H\033[J"

the ansi sequence to clear the screen.
Or so you would hope (however, that is *not* what you have listed!).

Unfortunately, it is poor practice to hard code such sequences.

I was bitten by that shortly after I started shell scripting.
However, since all such code was isolated in functions, converting
to a new terminal type was simple -- and quick.

These days, the ISO-6429 standard (almost the same as the older
ANSI x3.64) is so close to universal that I don't bother writing
for anything else any more. If the need arises, I'll do it, but it
will be simple to do, and much faster (both in coding and script
execution) than trying to accommodate all terminals from the start.
Instead the proper sequence should be obtained from the
appropriate database (TERMINFO or TERMCAP), and the easy way to
do that is,

tput clear

I still have a system which does not have tput.

--
Chris F.A. Johnson, author | <http://cfaj.freeshell. org>
Shell Scripting Recipes: | My code in this post, if any,
A Problem-Solution Approach | is released under the
2005, Apress | GNU General Public Licence

[Floyd L. Davidson]

Keith Thompson <ks***@mib.or g> wrote:

fl***@apaflo.c om (Floyd L. Davidson) writes:

af******@gmail. com wrote:

If I may recommend an alternative,

print "\033[H\033[J"

the ansi sequence to clear the screen.
Or so you would hope (however, that is *not* what you have listed!).

Unfortunately, it is poor practice to hard code such sequences.
Instead the proper sequence should be obtained from the
appropriate database (TERMINFO or TERMCAP), and the easy way to
do that is,

tput clear

(Or "clear".)

But /clear/ merely uses "tput clear".
On the other hand, I think it's been at least a decade since I've used
a terminal or emulator that's not VT100-compatible (i.e., accepts ANSI
control sequences).

Of course, I'll run into one the day after I start writing code that
depends on that assumption.

However, if you check out the various TERMINFO database entries for an
assortment of "VT100-compatible" terminals, you *will* find variation!

Plus, if a user has customized a terminal database, for who knows what
reason...

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) fl***@apaflo.co m

[Chris F.A. Johnson]

On 2006-04-12, Floyd L. Davidson wrote:

Keith Thompson <ks***@mib.or g> wrote:

tput clear

(Or "clear".)

But /clear/ merely uses "tput clear".

Not on systems without tput.

--
Chris F.A. Johnson, author | <http://cfaj.freeshell. org>
Shell Scripting Recipes: | My code in this post, if any,
A Problem-Solution Approach | is released under the
2005, Apress | GNU General Public Licence

[jpd]

Begin <j4************ @xword.teksavvy .com>
On 2006-04-12, Chris F.A. Johnson <cf********@gma il.com> wrote:

These days, the ISO-6429 standard (almost the same as the older
ANSI x3.64) is so close to universal that I don't bother writing
for anything else any more.
Oh, wonderful. ``All the world's a vax^W^WISO-6429 compatible'' all over
again.

If the need arises, I'll do it, but it will be simple to do, and
much faster (both in coding and script execution) than trying to
accommodate all terminals from the start.
Yes, why use a perfectly good abstraction when you can hardcode stuff.

I still have a system which does not have tput.

And that justifies everything else. Of course.
--
j p d (at) d s b (dot) t u d e l f t (dot) n l .
This message was originally posted on Usenet in plain text.
Any other representation, additions, or changes do not have my
consent and may be a violation of international copyright law.

[Chris F.A. Johnson]

On 2006-04-12, jpd wrote:

Begin <j4************ @xword.teksavvy .com>
On 2006-04-12, Chris F.A. Johnson <cf********@gma il.com> wrote:

These days, the ISO-6429 standard (almost the same as the older
ANSI x3.64) is so close to universal that I don't bother writing
for anything else any more.

Oh, wonderful. ``All the world's a vax^W^WISO-6429 compatible'' all over
again.

If the need arises, I'll do it, but it will be simple to do, and
much faster (both in coding and script execution) than trying to
accommodate all terminals from the start.

Yes, why use a perfectly good abstraction when you can hardcode stuff.

If it were perfectly good, there would be no question; however,
it's not.

I still have a system which does not have tput.

And that justifies everything else. Of course.

If I want to write portable scripts, then yes, it does.

--
Chris F.A. Johnson, author | <http://cfaj.freeshell. org>
Shell Scripting Recipes: | My code in this post, if any,
A Problem-Solution Approach | is released under the
2005, Apress | GNU General Public Licence

[Floyd L. Davidson]

"Chris F.A. Johnson" <cf********@gma il.com> wrote:

On 2006-04-12, Floyd L. Davidson wrote:

Keith Thompson <ks***@mib.or g> wrote:

tput clear

(Or "clear".)

But /clear/ merely uses "tput clear".

Not on systems without tput.

Shoot that thing, and put it (and yourself) out of its misery.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) fl***@apaflo.co m

[Christos Georgiou]

On Wed, 12 Apr 2006 15:59:05 -0400, rumours say that "Chris F.A. Johnson"
<cf********@gma il.com> might have written:

I still have a system which does not have tput.

And that justifies everything else. Of course.

If I want to write portable scripts, then yes, it does.

Well, either port your system out of the window or port tput.c to your
system and then start writing "portable" scripts. tput is part of the POSIX
1003.1 standard, and guess what the 'P' stands for in POSIX.

If you insist, I will retort to using Terry Pratchett references.
--
TZOTZIOY, I speak England very best.
"Dear Paul,
please stop spamming us."
The Corinthians

[Chris F.A. Johnson]

On 2006-04-12, Christos Georgiou wrote:

On Wed, 12 Apr 2006 15:59:05 -0400, rumours say that "Chris F.A. Johnson"
<cf********@gm ail.com> might have written:

I still have a system which does not have tput.

And that justifies everything else. Of course.
If I want to write portable scripts, then yes, it does.

Well, either port your system out of the window or port tput.c to your
system and then start writing "portable" scripts. tput is part of the POSIX
1003.1 standard, and guess what the 'P' stands for in POSIX.

It may be part of the POSIX standard, but there's nothing in the
POSIX definition of tput that provides for cursor positioning or
font attributes. The only defined operands are clear, init and
reset.

In fact, my scripts are portable to other terminal types by use
of files for each terminal, generated with tput. Using a
different terminal is as easy as ". /usr/share/term-sh/$TERM" or
something similar. I generated a lot of files a few years ago,
but I have never had any call for them, so I'd have to hunt for
them.
If you insist, I will retort to using Terry Pratchett references.

UNCLE!

--
Chris F.A. Johnson, author | <http://cfaj.freeshell. org>
Shell Scripting Recipes: | My code in this post, if any,
A Problem-Solution Approach | is released under the
2005, Apress | GNU General Public Licence

[Barry Margolin]

In article <go************ @xword.teksavvy .com>,
"Chris F.A. Johnson" <cf********@gma il.com> wrote:

In fact, my scripts are portable to other terminal types by use
of files for each terminal, generated with tput. Using a
different terminal is as easy as ". /usr/share/term-sh/$TERM" or
something similar. I generated a lot of files a few years ago,
but I have never had any call for them, so I'd have to hunt for
them.

So you've essentially reinvented the whole termcap/terminfo mechanism?

--
Barry Margolin, ba****@alum.mit .edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***