Is there a list of which features were added to specific releases (versions) of Bash?

Here are some links to official Bash documentation:

A more extensive list than the one below can be found at http://wiki.bash-hackers.org/scripting/bashchanges

Notable changes in released bash versions

Feature

Added in version

Copied/inspired from

PROMPT_COMMAND may be an array

5.1 (2020)

SRANDOM (variable)

5.1 (2020)

wait -p varname

5.1 (2020)

${var@U}, ${var@u}, ${var@L}, ${var@K}

5.1 (2020)

BASH_ARGV0 (variable)

5.0 (2019)

EPOCHSECONDS, EPOCHREALTIME (variables)

5.0 (2019)

zsh (2003, 2011)

wait -f

5.0 (2019)

history -d allows negative offsets

5.0 (2019)

assoc_expand_once (shopt)

5.0 (2019)

localvar_inherit (shopt)

5.0 (2019)

PS0 (variable)

4.4 (2016)

native

loadable builtin deployment infrastructure

4.4 (2016)

ksh93 (1993)

mapfile/readarray -d

4.4 (2016)

native

--help for builtins

4.4 (2016)

ksh93 (2001, possibly earlier)

${var@a}, ${var@A}, ${var@E}, ${var@P}, ${var@Q}

4.4 (2016)

mksh (2012) for the syntax, zsh (1990s) for the feature

local -

4.4 (2016)

Almquist shell (1989)

$! and wait for process substitutions

4.4 (2016)

native

wait -n

4.3 (2014)

native

test -R

4.3 (2014)

ksh93 (1993)

test -v 'array[element]' (bug fix)

4.3 (2014)

ksh93 (1993)

declare/typeset -n and associated changes to ${!ref} and for..in

4.3 (2014)

ksh93 (1993)

array[-idx] (in assignments, read, unset, etc)

4.3 (2014)

zsh (1990s)

\uXXXX and \UXXXXXXXX

4.2 (2011)

zsh (2001)

declare -g

4.2 (2011)

zsh (1990s)

test -v

4.2 (2011)

ksh93 (2009)

printf %(fmt)T

4.2 (2011)

ksh93 (1999)

${array[-idx]} and ${var:start:-len}

4.2 (2011)

zsh (1990s) and native

lastpipe (shopt)

4.2 (2011)

ksh (1980s) default behaviour there

read -N

4.1 (2010)

ksh93 (2003)

{var}> or {var}< etc. (FD variable assignment)

4.1 (2010)

developed jointly with ksh93 and zsh

syslog history (compile option)

4.1 (2010)

native

complete -D (allowing dynamically loaded completions)

4.1 (2010)

BASH_XTRACEFD

4.1 (2010)

native

;& and ;;& fall-throughs for case

4.0 (2009)

ksh93 (1993)

associative arrays

4.0 (2009)

ksh93 (1993)

&>> and |&

4.0 (2009)

native and csh (1970s)

command_not_found_handle (function)

4.0 (2009)

native

compopt (builtin)

4.0 (2009)

coproc (keyword)

4.0 (2009)

ksh (1980s), zsh (1990) for the coproc keyword

globstar (shopt)

4.0 (2009)

zsh (1992), ksh93 (2005) for the name of the option

mapfile/readarray (builtin)

4.0 (2009)

native

${var,} ${var,,} ${var^} ${var^^}

4.0 (2009)

native

{009..012} (leading zeros in brace expansions)

4.0 (2009)

zsh (1995)

{x..y..incr}

4.0 (2009)

ksh93 (2005)

read -t 0 (test input availability)

4.0 (2009)

read -t 0.5

4.0 (2009)

zsh (2003)

read -i

4.0 (2009)

zsh (vared) (1990s)

x+=string array+=(string)

3.1 (2005)

ksh93 (2000)

printf -v var

3.1 (2005)

native

nocasematch (shopt)

3.1 (2005)

native

{x..y}

3.0 (2004)

zsh (1995)

${!array[@]}

3.0 (2004)

ksh93 (1993)

[[ =~

3.0 (2004)

native

printf %q produces $'...'

2.05b (2002)

ksh93 (1993)

[n]>&word- and [n]<&word-

2.05b (2002)

ksh93

<<<

2.05b (2002)

zsh (1991)

i++

2.04 (2000)

ksh93 (1993)

for ((;;))

2.04 (2000)

ksh93 (1993)

/dev/fd/N, /dev/tcp/host/port, etc.

2.04 (2000)

ksh93 (1993)

read -t, -n, -d and -s

2.04 (2000)

ksh93 (1993)

a=(*.txt) file expansion

2.03 (1999)

ksh93 (1993)

extglob (shopt)

2.02 (1998)

ksh (1980s)

[[

2.02 (1998)

ksh (1980s)

printf (builtin)

2.02 (1998)

ksh (1980s)

$(< filename)

2.02 (1998)

ksh (1980s)

** (exponentiation)

2.02 (1998)

zsh (1994)

\xNN

2.02 (1998)

zsh (1994 or earlier)

(( ))

2.0 (1996)

ksh (1980s)

arrays

2.0 (1996)

ksh (1980s)

$'...' (new quoting syntax)

2.0 (1996)

ksh93 (1993)

List of bash releases and other notable events

Release

Date

bash-5.1

2020-12-07

bash-5.0

2019-01-07

bash-4.4

2016-09-16

Shellshock patches are released for bash-2.05b through bash-4.3

2014-09-24 to 2014-10-05

bash-4.3

2014-02-27

bash-4.2

2011-02-14

bash-4.1

2010-01-02

bash-4.0

2009-02-23

bash-3.2

2006-10-12

bash-3.1

2005-12-09

bash-3.0

2004-07-27

bash-2.05b

2002-07-17

bash-2.05a

2001-11-15

bash-2.05

2001-04-09

bash-2.04

http://ftp.gnu.org/gnu/bash puts it around 2000-03-21

bash-2.03

1999-02-19

bash-2.02

1998-04-20

bash-2.01

1997-06-06

bash-2.0

1996-12-23

bash-1.14

1994-06-02

bash-1.13

1993-09-03

Looks like Chet Ramey takes over as maintainer between 1.12 and 1.13

bash-1.12

1992-01-26

bash-1.11

1992-01-10

bash-1.10

First mention found at 1991-10-07, so some time before that

bash-1.09

First mention found at 1991-06-02

bash-1.08

1991-05-22

bash-1.07

likely 1991-02-01

bash-1.06

This is a tough one. There was apparently a "bootleg" version of 1.06, so this requires more digging

bash-1.05

1990-03-03

bash-1.04

First mention found at 1989-11-07

bash-1.03

1989-09-02

bash-1.02

First mention found at 1989-07-09

bash-1.01

1989-06-23

bash-1.00

Hard to search for ...

bash-0.99

First beta release 1989-06-7