On 11/20/24 10:31 AM, Martin D Kealey wrote:
On Wed, 20 Nov 2024, 07:36 Paul Eggert, <egg...@cs.ucla.edu <mailto:egg...@cs.ucla.edu>> wrote:However, I don't see why Bash should differ from POSIX behavior. Bash already diagnoses "printf %d x" and "printf %d ' '"; why should it be silent about "printf %d ''"? From a semantic perspective, because "" doesn't contain any non-digits.
POSIX says this doesn't matter, it's whether or not the argument can be `completely converted': "If an argument operand cannot be completely converted into an internal value appropriate to the corresponding conversion specification, a diagnostic message shall be written to standard error and the utility shall not exit with a zero exit status..." The question is what `completely converted' means here. As for the argument itself, it has to be "an unsuffixed C integer constant as as described by the ISO C standard", which requires at least one digit (or letter for hex constants).
From an implementation perspective, the standard check for a valid number is to call strtol() (or similar) and then see if there are any non-digits remaining. It takes an extra check to see if it stopped without processing any digits.
If you want to use strtol() as a reference, POSIX says that it doesn't perform any conversion if the string is null: "If the subject sequence is empty or does not have the expected form, no conversion is performed; the value of nptr shall be stored in the object pointed to by endptr, provided that endptr is not a null pointer." So that can reasonably mean "not completely converted."
I'm in favour of treating the empty token (string) as being a valid way to write zero, in the same way that 00 and 0000000 are also valid ways to write zero. That makes it more consistent in ways that are useful.
I don't think being able to write "$var" without checking whether or not
var is unset or null is compelling enough.
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU c...@case.edu http://tiswww.cwru.edu/~chet/
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