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Top Forums UNIX for Dummies Questions & Answers Python... Post 302821925 by bakunin on Sunday 16th of June 2013 06:15:21 AM

06-16-2013

Registered User

Quote:

Originally Posted by wisecracker

I had no idea that the transient command structure was dynamic and that there is a minimal requirement.

Every command is a single executable. When you type "ls" you invoke "/usr/bin/ls", which is a program in its own right, quite as any other program. Now there might be a package "basic.commands", which bundles "ls" with other, similarily ubiquitous commands, but that doesn't have to be so. You could remove "/usr/bin/ls" from a system with no other consequence than not being able to list directories/files.

Now, there is a list of programs ("commands"), which is described in the POSIX documents as "mandatory". That means, if a systems calls itself "UNIX" it can be expected to have these programs. "ls" is part of this list, as is "awk", "sed", "sh", etc.. These commands should be installed wether or not they are actually used in a script running on this system. The same goes for libraries, interfaces, system calls, and similar functions of the system. All these are described in the POSIX documents. For the example "ls" this would mean there is a description about which commandlne options it has to understand and what exactly these options will make "ls" do when invoked.

Everything else is installed on top of that, but it is not "UNIX", just very common. That goes for "perl" as well as "gzip" and "ssh" and whatnot. These are quite common tools, but not "part of the UNIX system". It was once quite common to have these annoying nodding sausage dogs in the back of a car, but just because these are (or were) quite common doesn't mean they were "part of the system 'automobile'", like the steering wheel or the brake.

I hope this helps.

bakunin

bakunin

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perl

perl(1) 						      General Commands Manual							   perl(1)

NAME

       perl - Practical Extraction and Report Language

DESCRIPTION

       The  perl  software  is unsupported software that is provided as part of Tru64 UNIX.  Compaq will fix problems in this unsupported software
       only if they are specific to Tru64 UNIX.  Compaq will not fix problems that are integral to the software itself or that occur when the com-
       ponent is used on UNIX systems other than Tru64 UNIX.  Compaq will not add functionality to this software.

       Except  for this reference page, other reference pages that Tru64 UNIX supplies for perl are passed through without changes.  The reference
       pages distributed as part of this software are available in the directories  /usr/share/doclib/annex/man/man[1-9].   You  should  use  this
       directory stem in the man command or add it to the MANPATH environment variable to make these files available to the man command.

									  Note

       Compaq  is  not	responsible  for the content or quality of reference pages and other documents installed under the /usr/share/doclib/annex
       directory  and  does  not  revise  this	material  in  response	to  customer  problem  reports.  Reference  pages  installed   under   the
       /usr/share/doclib/annex/man directory are not available from Compaq in book form; for example, they are not included in the reference manu-
       als that you receive when you order the Tru64 UNIX documentation set as hard copy books.

       Problems related to the content or quality of any documentation installed in the /usr/share/doclib/annex directory tree should be  sent	to
       the developers of the documentation.

       The format for changing the search path with the man command is: man -P /usr/share/doclib/annex/man [section] title...

       If  you	are  using  the  Bourne,  Korn,  or  POSIX  shells,  use  the following command sequence to modify your environment: MANPATH=$MAN-
       PATH:/usr/share/doclib/annex/man export MANPATH

       If you are using the C shell, enter the command: setenv MANPATH `echo $MANPATH`:/usr/share/doclib/annex/man

       See the reference pages for the man(1) command for additional information on the search path used to locate files.

       The reference pages associated with this product are not included in the whatis data base created by the catman	command.   Therefore,  the
       man -k and apropos commands will not locate reference pages included with this product.

SEE ALSO

       Commands:  apropos(1), catman(8), man(1)

																	   perl(1)