Starting Bash with the `--posix' command-line option or executing `set
-o posix' while Bash is running will cause Bash to conform more closely
-to the POSIX.2 standard by changing the behavior to match that
-specified by POSIX.2 in areas where the Bash default differs.
+to the POSIX 1003.2 standard by changing the behavior to match that
+specified by POSIX in areas where the Bash default differs.
The following list is what's changed when `POSIX mode' is in effect:
4. Reserved words may not be aliased.
- 5. The POSIX.2 `PS1' and `PS2' expansions of `!' to the history
+ 5. The POSIX 1003.2 `PS1' and `PS2' expansions of `!' to the history
number and `!!' to `!' are enabled, and parameter expansion is
- performed on the value regardless of the setting of the
- `promptvars' option.
+ performed on the values of `PS1' and `PS2' regardless of the
+ setting of the `promptvars' option.
- 6. Interactive comments are enabled by default. (Note that Bash has
- them on by default anyway.)
+ 6. Interactive comments are enabled by default. (Bash has them on by
+ default anyway.)
- 7. The POSIX.2 startup files are executed (`$ENV') rather than the
- normal Bash files.
+ 7. The POSIX 1003.2 startup files are executed (`$ENV') rather than
+ the normal Bash files.
8. Tilde expansion is only performed on assignments preceding a
command name, rather than on all assignment statements on the line.
11. Non-interactive shells exit if FILENAME in `.' FILENAME is not
found.
- 12. Redirection operators do not perform filename expansion on the word
+ 12. Non-interactive shells exit if a syntax error in an arithmetic
+ expansion results in an invalid expression.
+
+ 13. Redirection operators do not perform filename expansion on the word
in the redirection unless the shell is interactive.
- 13. Function names must be valid shell `name's. That is, they may not
+ 14. Redirection operators do not perform word splitting on the word in
+ the redirection.
+
+ 15. Function names must be valid shell `name's. That is, they may not
contain characters other than letters, digits, and underscores, and
- may not start with a digit. Declaring a function with an illegal
+ may not start with a digit. Declaring a function with an invalid
name causes a fatal syntax error in non-interactive shells.
- 14. POSIX.2 `special' builtins are found before shell functions during
- command lookup.
+ 16. POSIX 1003.2 `special' builtins are found before shell functions
+ during command lookup.
- 15. If a POSIX.2 special builtin returns an error status, a
+ 17. If a POSIX 1003.2 special builtin returns an error status, a
non-interactive shell exits. The fatal errors are those listed in
the POSIX.2 standard, and include things like passing incorrect
options, redirection errors, variable assignment errors for
assignments preceding the command name, and so on.
- 16. If the `cd' builtin finds a directory to change to using
+ 18. If the `cd' builtin finds a directory to change to using
`$CDPATH', the value it assigns to the `PWD' variable does not
contain any symbolic links, as if `cd -P' had been executed.
- 17. A non-interactive shell exits with an error status if a variable
+ 19. If `$CDPATH' is set, the `cd' builtin will not implicitly append
+ the current directory to it. This means that `cd' will fail if no
+ valid directory name can be constructed from any of the entries in
+ `$CDPATH', even if the a directory with the same name as the name
+ given as an argument to `cd' exists in the current directory.
+
+ 20. A non-interactive shell exits with an error status if a variable
assignment error occurs when no command name follows the assignment
statements. A variable assignment error occurs, for example, when
- trying to assign a value to a read-only variable.
+ trying to assign a value to a readonly variable.
- 18. A non-interactive shell exits with an error status if the iteration
+ 21. A non-interactive shell exits with an error status if the iteration
variable in a `for' statement or the selection variable in a
- `select' statement is a read-only variable.
+ `select' statement is a readonly variable.
+
+ 22. Process substitution is not available.
- 19. Process substitution is not available.
+ 23. Assignment statements preceding POSIX 1003.2 special builtins
+ persist in the shell environment after the builtin completes.
- 20. Assignment statements preceding POSIX.2 `special' builtins persist
- in the shell environment after the builtin completes.
+ 24. The `export' and `readonly' builtin commands display their output
+ in the format required by POSIX 1003.2.
-There is other POSIX.2 behavior that Bash does not implement.
+There is other POSIX 1003.2 behavior that Bash does not implement.
Specifically:
1. Assignment statements affect the execution environment of all
projects / platform / upstream / bash.git / blobdiff