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Full Discussion: while read issue
Top Forums Shell Programming and Scripting while read issue Post 302700161 by bakunin on Thursday 13th of September 2012 04:52:28 AM
Old 09-13-2012
Quote:
Originally Posted by cfajohnson
There is nothing in the script that is shell or OS specific, so the shell and the OS are both irrelevant.
Across implementations in different OSes ksh might either be ksh88 or ksh93, which exhibit differences regarding the treatment of "echo". Furthermore, if "/bin/echo" is found in the PATH, ksh treats its own built-in differently, even if it is there. With bash the situation may or may not be that complicated, but i lack experience with all bash-implementations there may be, so i can't say for sure.

Therefore my opinion is that knowing the OS and the shell thread-opener talks about may or may not matter. I can only decide once i know these, not beforehand.

Quote:
In all shells, echo adds a newline.
In some shells "echo" is not a built-in but a call to "/bin/echo". If the implentation of each respective OS does or doesn't add a newline i don't know. I haven't used each and every Unix-like system there is.

Quote:
Neither echo nor print is a good idea.

Use printf; it is the only portable method.
With Korn shell "print" is a built-in and is preferred. (see here) With bash "echo" is a built-in and is probably preferred too (not so sure as i don't use bash more than i have to, but most bash scripts i have seen use "echo" for that purpose).

To ask for "portability" in general without specifying where you would want to port it is completely arbitrary: in general it is a good idea to write scripts in a way so that they work on as many systems as possible with as few changes as possible. To ask for a ksh script that it has to work in bash (or vice versa) makes about as much sense as asking for a FORTRAN program to compile on a C-compiler without error.

Again, i don't say portability should not be an issue. But "portability" as a goal makes only sense if there is a reference platform/shell/environment defined to which it should be portable. Without such a definition it is just a buzzword.

Probably you imply POSIX as this reference here and mean "portability towards the POSIX-specification", which is as good a goal as any else. If the thread-opener has POSIX-compatible systems and might face the necessity to port the script from one of these POSIX-compatible systems to another then you are right - on the other hand, if he has another set of systems he might be better off to enforce compatibility between the systems he actually has than towards a generic standard some of his systems do not adhere to.

Insofar it would also be a good idea to know more about his actual environment instead of declaring this "irrelevant" like above.

I hope this helps.

bakunin
 

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LEARN ABOUT SUNOS

script

script(1)							   User Commands							 script(1)

NAME

       script - make record of a terminal session

SYNOPSIS

       script [-a] [filename]

DESCRIPTION

       The  script  utility  makes a record of everything printed on your screen. The record is written to filename. If no file name is given, the
       record is saved in the file typescript. See WARNINGS.

       The script command forks and creates a sub-shell, according to the value of $SHELL, and records the text from this session. The script ends
       when the forked shell exits or when Control-d is typed.

OPTIONS

       The following option is supported:

       -a	Appends the session record to filename, rather than overwriting it.

NOTES

       script places everything that appears on the screen in filename, including prompts.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+
       |CSI			     |Enabled			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       attributes(5)

WARNINGS

       script  can  pose  a  security risk when used in directories that are writable by other users (for example, /tmp), especially when run by a
       privileged user, that is, root. Be sure that typescript is not a link before running script.

SunOS 5.10							    30 Jan 2004 							 script(1)
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