-Starting bash with the `-posix' command-line option or setting the variable
-POSIXLY_CORRECT 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.
+Bash POSIX Mode
+===============
-The following list is what's changed when `posixly_correct' is enabled:
+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.
-1. When a command in the hash table no longer exists, bash will re-search
- $PATH to find the new location.
+The following list is what's changed when `POSIX mode' is in effect:
-2. The >& redirection does not redirect stdout and stderr.
+ 1. When a command in the hash table no longer exists, Bash will
+ re-search `$PATH' to find the new location. This is also
+ available with `shopt -s checkhash'.
-3. The message printed by the job control code and builtins when a job
- exits with a non-zero status is `Done(status)'.
+ 2. The `>&' redirection does not redirect stdout and stderr.
-4. The <> redirection does not open a file for both stdin and stdout, but
- rather opens it for read-write on fd 0.
+ 3. The message printed by the job control code and builtins when a job
+ exits with a non-zero status is `Done(status)'.
-5. Reserved words may not be aliased.
+ 4. Reserved words may not be aliased.
-6. The Posix.2 PS1 and PS2 expansions of `!' -> history number and `!!' -> `!'
- are enabled.
+ 5. The POSIX.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.
-7. Interactive comments are enabled by default. (Note that this version has
- them on by default anyway.)
+ 6. Interactive comments are enabled by default. (Note that Bash has
+ them on by default anyway.)
-8. The Posix.2 startup files are executed ($ENV) rather than the normal bash
- files.
+ 7. The POSIX.2 startup files are executed (`$ENV') rather than the
+ normal Bash files.
-9. Tilde expansion is only performed on assignments preceding a command name,
- rather than on all assignment statements on the line.
+ 8. Tilde expansion is only performed on assignments preceding a
+ command name, rather than on all assignment statements on the line.
-10. The default history file is ~/.sh_history (default value of $HISTFILE).
+ 9. The default history file is `~/.sh_history' (this is the default
+ value of `$HISTFILE').
-11. The output of `kill -l' prints all the signal names on a single line,
- separated by spaces.
+ 10. The output of `kill -l' prints all the signal names on a single
+ line, separated by spaces.
-12. Non-interactive shells exit if `file' in `. file' is not found.
+ 11. Non-interactive shells exit if FILENAME in `.' FILENAME is not
+ found.
-13. Redirection operators do not perform pathname expansion on the word
- in the redirection unless the shell is interactive
+ 12. Redirection operators do not perform filename expansion on the word
+ in the redirection unless the shell is interactive.
-14. Function names must be valid shell identifiers. That is, they may not
- contain characters other than letters, digits, and underscores, and
- may not start with a digit
+ 13. 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
+ name causes a fatal syntax error in non-interactive shells.
-There is other Posix.2 behavior that bash does not implement. Specifically:
+ 14. POSIX.2 `special' builtins are found before shell functions during
+ command lookup.
-1. There are no `special builtins' and `regular builtins'. All builtins
- are equivalent. This means that:
+ 15. If a POSIX.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.
- o assignment statements affect the execution environment of all
- builtins, not just special ones
- o temporary assignments do not persist after Posix.2 special
- builtins complete
- o Functions are found before Posix.2 special builtins
- o The shell does not exit upon errors while executing Posix.2
- special builtins
+ 16. 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.
-2. $LINENO does not represent the line number of a command within a function
+ 17. 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.
+
+ 18. 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.
+
+ 19. Process substitution is not available.
+
+ 20. Assignment statements preceding POSIX.2 `special' builtins persist
+ in the shell environment after the builtin completes.
+
+
+There is other POSIX.2 behavior that Bash does not implement.
+Specifically:
+
+ 1. Assignment statements affect the execution environment of all
+ builtins, not just special ones.
-3. The arithmetic evaluator does not implement the `e ? e1 : e2' conditional
- expression
projects / platform / upstream / bash.git / blobdiff