$LINENO within functions

[Oliver Fromme]

Stefan Farfeleder wrote:
 > SUSv3 says the following about $LINENO:
 > 
 > "Set by the shell to a decimal number representing the current
 > sequential line number (numbered starting with 1) within a script or
 > function before it executes each command. If the user unsets or resets
 > LINENO , the variable may lose its special meaning for the life of the
 > shell. If the shell is not currently executing a script or function, the
 > value of LINENO is unspecified. This volume of IEEE Std 1003.1-2001
 > specifies the effects of the variable only for systems supporting the
 > User Portability Utilities option."
 > 
 > My initial interpretation of "or function" was that it means $LINENO
 > within a function should be relative to the function's beginning line.
 > Now I'm not so sure anymore.  Bash release 2.05b changed the expansion
 > of $LINENO within functions to absolute numbering, stating this is
 > required by POSIX.  But then I wonder about the meaning of "or
 > function".  Does it mean functions in interactive scripts?  Because for
 > functions in shell scripts the mentioning of both "script" and
 > "function" seems redundant.

When reading the SUSv3 text, my interpretation is the same
as your initial interpretation.  FWIW, Solaris' POSIX shell
(ksh) behaves like FreeBSD's sh, not like bash.  Same for
zsh.  So bash seems to be pretty much alone in its inter-
pretation of SUSv3.

I also think that it should not make a difference whether a
function definition is entered interactively or read from
a script -- $LINENO should always expand to the same value
at the same line number within that function.  It shouldn't
depend on where the function definition comes from.
I think that's what the people from the SUS/POSIX committee
wanted to say.

Therefore my opinion is that FreeBSD's current behaviour is
fine, and bash is wrong.

By the way, SUSv3 also mentions $LINENO in the Shell Command
Language Rationale (xrat/xcu_chap02) in the explanation of
the $PS4 variable used for debugging with "set -x":

=== QUOTE ===

   PS4     This variable is used for shell debugging.
           For example, the following script:

 PS4='[${LINENO}]+ '
 set -x
 echo Hello

           writes the following to standard error:

 [3]+ echo Hello

=== /QUOTE ===

I'm not sure which behaviour makes more sense here.  It
depends on how you look at it, I guess.

Best regards
   Oliver

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