diff options
Diffstat (limited to 'README')
| -rw-r--r-- | README | 29 |
1 files changed, 25 insertions, 4 deletions
diff --git a/README b/README index 034f5f39a..f8a7cf241 100644 --- a/README +++ b/README @@ -45,6 +45,31 @@ behaviour.) Now it is treated identically to "$@". The same change applies to expressions with forced splitting such as ${=1+"$@"}, but otherwise the case where SH_WORD_SPLIT is not set is unaffected. +In previous versions of the shell it was possible to use index 0 in an +array or string subscript to refer to the same element as index 1 if the +option KSH_ARRAYS was not in effect. This was a limited approximation to +the full KSH_ARRAYS handling and so was not very useful. In this version +of the shell, this behaviour is only provided when the option +KSH_ZERO_SUBSCRIPT is set. Note that despite the name this does not provide +true compatibility with ksh or other shells and KSH_ARRAYS should still be +used for that purpose. By default, the option is not set; an array +subscript that evaluates to 0 returns an empty string or array element and +attempts to write to an array or string range including only a zero +subscript are treated as an error. Writes to otherwise valid ranges that +also include index zero are allowed; hence for example the assignment + array[(R)notfound,(r)notfound]=() +(where the string "notfound" does not match an element in $array) sets the +entire array to be empty, as in previous versions of the shell. +KSH_ZERO_SUBSCRIPT is irrelevant when KSH_ARRAYS is set. Also as in previous +versions, attempts to write to non-existent elements at the end of an array +cause the array to be suitably extended. This difference means that, for +example + array[(R)notfound]=(replacement) +is an error if KSH_ZERO_SUBSCRIPT is not set (new behaviour), while + array[(r)notfound]=(replacement) +causes the given value to be appended to the array (same behaviour as +previous versions). + The "exec" precommand modifier now takes various options for compatibility with other shells. This means that whereas "exec -prog" previously tried to execute a command name "-prog", it will now report an error @@ -77,10 +102,6 @@ of the value. The form ${param//#$search/replace} where the value $search starts with "%" considers the "%" to be part of the search string as before. -Parameter subscripts of the form ${array[(R)test]} now return the -empty string if they fail to match. The previous longstanding behaviour -was confusing and useless. - The MULTIBYTE option is on by default where it is available; this causes many operations to recognise characters as in the current locale. Older versions of the shell always assumed a character was one byte. |