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Full Discussion: Possible ksh93 Bug Expanding Variables?
Top Forums Shell Programming and Scripting Possible ksh93 Bug Expanding Variables? Post 303000061 by Don Cragun on Monday 3rd of July 2017 06:36:27 PM
Old 07-03-2017
You are hoping the backslash in the expansion of ${chLine#?} will be treated as a literal backslash character. And, in the expansion of ${chLine} it is. But, in word in ${chLine%word} the backslash is an escape character. Since \# is treated as an escaped # in the pattern instead of the two character literal \#, there is no match and the string isn't removed from the expansion with the removal of a matching smallest suffix pattern.

This is one of the changes that was made to ksh88 behavior (that is handled differently in ksh93) while the POSIX shell standard was being developed.

I think this explains the difference you're seeing, but unless your script tests which version of ksh you're using and uses different code for the two cases, you may have trouble finding a common variable expansion that will get you what you want in both versions of the shell. Unfortunately, you can't use ${chLine:2} in ksh88 (but it gives you what you want in ksh93).
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LEARN ABOUT DEBIAN

shcomp

SHCOMP(1)						    User Environment Utilities							 SHCOMP(1)

NAME

       shcomp - compile a ksh93 shell script

SYNOPSIS

       shcomp [ options ] [infile] [outfile]]

ORIGIN OF THIS MAN PAGE

       This man page was written by Christophe Martin <Schplurtz@free.fr> for the Debian GNU/Linux system. It is based on "shcomp --man" output.

DESCRIPTION

       Unless  -D  is  specified,  shcomp takes a shell script, infile, and creates a binary format file, outfile, that ksh93 can read and execute
       with the same effect as the original script.

       Since aliases are processed as the script is read, alias definitions whose value requires variable expansion will not work correctly.

       If -D is specified, all double quoted strings that are preceded by $ are output. These are the messages	that  need  to	be  translated	to
       locale specific versions for internationalization.

       If  outfile is omitted, then the results will be written to standard output.  If infile is also omitted, the shell script will be read from
       standard input.

OPTIONS

       -D, --dictionary
	      Generate a list of strings that need to be placed in a message catalog for internationalization.

       -n, --noexec
	      Displays warning messages for obsolete or non-conforming constructs.

       -v, --verbose
	      Displays input from infile onto standard error as it reads it.

       --man  Displays this man page on standard error and exits.

       --help Shows a short help message and exits.

EXIT STATUS

       0      Successful completion.

       >0     An error occurred.

DEBIAN WARNING

       On a Debian GNU/Linux system, more than one package may provide ksh. the output of shcomp can only be used by ksh93.  Any other ksh will be
       unable to run the compiled script.

EXAMPLE

       ( echo '#! /bin/ksh93' ; shcomp myscript ) > myscript.bin &&
       chmod 755 myscript.bin
       ./myscript.bin

SEE ALSO

       ksh(1)

IMPLEMENTATION

       version	       shcomp (AT&T Labs Research) 2012-02-29
       author	       David Korn <dgk@research.att.com>
       copyright       Copyright (c) 1982-2012 AT&T Intellectual Property
       license	       http://www.eclipse.org/org/documents/epl-v10.html

KSH93								  Fri Jun 3 2005							 SHCOMP(1)
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