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https://https.git.savannah.gnu.org/git/bash.git
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Chet Ramey
92 lines
3.8 KiB
Plaintext
92 lines
3.8 KiB
Plaintext
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1. New Features in Bash
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a. `exec -a foo' now sets $0 to `foo' in an executable shell script without a
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leading #!.
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b. Subshells begun to execute command substitutions or run shell functions or
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builtins in subshells do not reset trap strings until a new trap is
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specified. This allows $(trap) to display the caller's traps and the
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trap strings to persist until a new trap is set.
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c. `trap -p' will now show signals ignored at shell startup, though their
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disposition still cannot be modified.
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d. $'...', echo, and printf understand \uXXXX and \UXXXXXXXX escape sequences.
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e. declare/typeset has a new `-g' option, which creates variables in the
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global scope even when run in a shell function.
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f. test/[/[[ have a new -v variable unary operator, which returns success if
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`variable' has been set.
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g. Posix parsing changes to allow `! time command' and multiple consecutive
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instances of `!' (which toggle) and `time' (which have no cumulative
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effect).
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h. Posix change to allow `time' as a command by itself to print the elapsed
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user, system, and real times for the shell and its children.
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j. $((...)) is always parsed as an arithmetic expansion first, instead of as
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a potential nested command substitution, as Posix requires.
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k. A new FUNCNEST variable to allow the user to control the maximum shell
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function nesting (recursive execution) level.
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l. The mapfile builtin now supplies a third argument to the callback command:
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the line about to be assigned to the supplied array index.
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m. The printf builtin has a new %(fmt)T specifier, which allows time values
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to use strftime-like formatting.
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n. There is a new `compat41' shell option.
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o. The cd builtin has a new Posix-mandated `-e' option.
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p. Negative subscripts to indexed arrays, previously errors, now are treated
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as offsets from the maximum assigned index + 1.
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q. Negative length specifications in the ${var:offset:length} expansion,
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previously errors, are now treated as offsets from the end of the variable.
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r. Parsing change to allow `time -p --'.
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s. Posix-mode parsing change to not recognize `time' as a keyword if the
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following token begins with a `-'. This means no more Posix-mode
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`time -p'. Posix interpretation 267.
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t. There is a new `lastpipe' shell option that runs the last command of a
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pipeline in the current shell context. The lastpipe option has no
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effect if job control is enabled.
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u. History expansion no longer expands the `$!' variable expansion.
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v. Posix mode shells no longer exit if a variable assignment error occurs
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with an assignment preceding a command that is not a special builtin.
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w. Non-interactive mode shells exit if -u is enabled and an attempt is made
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to use an unset variable with the % or # expansions, the `//', `^', or
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`,' expansions, or the parameter length expansion.
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x. Posix-mode shells use the argument passed to `.' as-is if a $PATH search
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fails, effectively searching the current directory. Posix-2008 change.
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2. New Features in Readline
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a. The history library does not try to write the history filename in the
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current directory if $HOME is unset. This closes a potential security
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problem if the application does not specify a history filename.
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b. New bindable variable `completion-display-width' to set the number of
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columns used when displaying completions.
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c. New bindable variable `completion-case-map' to cause case-insensitive
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completion to treat `-' and `_' as identical.
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d. There are new bindable vi-mode command names to avoid readline's case-
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insensitive matching not allowing them to be bound separately.
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e. New bindable variable `menu-complete-display-prefix' causes the menu
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completion code to display the common prefix of the possible completions
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before cycling through the list, instead of after.
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