37. Bash-4.0 now allows SIGCHLD to interrupt the wait builtin, as Posix
specifies, so the SIGCHLD trap is no longer always invoked once per
- exiting child if you are using `wait' to wait for all children.
+ exiting child if you are using `wait' to wait for all children. As
+ of bash-4.2, this is the status quo only when in posix mode.
38. Since bash-4.0 now follows Posix rules for finding the closing delimiter
of a $() command substitution, it will not behave as previous versions
44. Bash-4.1 uses the current locale when comparing strings using the < and
> operators to the `[[' command. This can be reverted to the previous
- behavior by setting one of the `compatNN' shopt options.
+ behavior (ASCII collating and strcmp(3)) by setting one of the
+ `compatNN' shopt options, where NN is less than 41.
+
+45. Command substitutions now remove the caller's trap strings when trap is
+ run to set a new trap in the subshell. Previous to bash-4.2, the old
+ trap strings persisted even though the actual signal handlers were reset.
+
+46. When in Posix mode, a single quote is not treated specially in a
+ double-quoted ${...} expansion, unless the expansion operator is
+ # or % or the new `//', `^', or `,' expansions. In particular, it
+ does not define a new quoting context. This is from Posix interpretation
+ 221.
+
+47. Posix mode shells no longer exit if a variable assignment error occurs
+ with an assignment preceding a command that is not a special builtin.
+
Shell Compatibility Level
=========================
Bash-4.0 introduced the concept of a `shell compatibility level', specified
-as a set of options to the shopt builtin (compat31, compat32, compat40 at
-this writing). There is only one current compatibility level -- each
-option is mutually exclusive. This list does not mention behavior that is
-standard for a particular version (e.g., setting compat32 means that quoting
-the rhs of the regexp matching operator quotes special regexp characters in
-the word, which is default behavior in bash-3.2 and above).
+as a set of options to the shopt builtin (compat31, compat32, compat40, and
+compat41 at this writing). There is only one current compatibility level --
+each option is mutually exclusive. This list does not mention behavior
+that is standard for a particular version (e.g., setting compat32 means that
+quoting the rhs of the regexp matching operator quotes special regexp
+characters in the word, which is default behavior in bash-3.2 and above).
compat31 set
- the < and > operators to the [[ command do not consider the current
- locale when comparing strings
+ locale when comparing strings; they use ASCII ordering
- quoting the rhs of the regexp matching operator (=~) has no
special effect
compat32 set
- the < and > operators to the [[ command do not consider the current
- locale when comparing strings
+ locale when comparing strings; they use ASCII ordering
compat40 set
- the < and > operators to the [[ command do not consider the current
- locale when comparing strings
+ locale when comparing strings; they use ASCII ordering
- interrupting a command list such as "a ; b ; c" causes the execution
- of the entire list to be aborted
+ of the entire list to be aborted (in versions before bash-4.0,
+ interrupting one command in a list caused the next to be executed)
+compat41 set
+ - interrupting a command list such as "a ; b ; c" causes the execution
+ of the entire list to be aborted (in versions before bash-4.0,
+ interrupting one command in a list caused the next to be executed)
+ - when in posix mode, single quotes in the `word' portion of a
+ double-quoted parameter expansion define a new quoting context and
+ are treated specially
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