re: GNU bash, version 5.2.37(1)-release (aarch64-apple-darwin23.4.0) ---
1) `shopt compat50` does not exist. The manpage does specify that 'compat50' is a valid option for `shopt` under BUILTINS/shopt. Yet bash provides an error when trying to read or change it: > shopt compat50 bash: shopt: compat50: invalid shell option name "Bash-5.0 is the final version for which there will be an individual shopt option for the previous version. Users should use BASH_COMPAT on bash-5.0 and later versions." ...Not sure if this means `shopt compat50` should work or not. But either way, `shopt compat50` should be consistent with BUILTINS/shopt. --- 2) Bash errors on valid BASH_COMPAT values? Am I missing something here? "BASH_COMPAT...For example, 4.2 and 42 are valid values that correspond to the compat42 shopt option and set the compatibility level to 42. The current version is also a valid value." > BASH_COMPAT=4.4 bash --noprofile -l bash: BASH_COMPAT: compat44: compatibility value out of range bash-5.2$ shopt compat44 compat44 on > BASH_COMPAT=44 bash --noprofile -l bash: BASH_COMPAT: compat44: compatibility value out of range bash-5.2$ shopt compat44 compat44 on > BASH_COMPAT=compat44 bash --noprofile -l bash: BASH_COMPAT: compat44: compatibility value out of range bash: BASH_COMPAT: compat44: compatibility value out of range bash-5.2$ shopt compat44 compat44 off # ^-- as expected, just showing for completeness > bash --noprofile -l bash-5.2$ shopt compat44 compat44 off bash-5.2$ BASH_COMPAT=44 bash-5.2$ shopt compat44 compat44 on bash-5.2$ BASH_COMPAT= bash-5.2$ shopt compat44 compat44 off bash-5.2$ BASH_COMPAT=4.4 bash-5.2$ shopt compat44 compat44 on bash-5.2$ BASH_COMPAT= bash-5.2$ shopt compat44 compat44 off bash-5.2$ BASH_COMPAT=compat44 bash: BASH_COMPAT: compat44: compatibility value out of range # ^-- again, as expected, just showing for completeness --- For convenience, here is an abridged excerpt of the manpage. Line numbers correspond with this set of commands: LESS="-JN -x4 --line-num-width=4 --status-col-width=1 --use-color" MANPAGER="less -sR" MANWIDTH=75 man bash 714 PARAMETERS 848 Shell Variables 849 The following variables are set by the shell: 1167 BASH_COMPAT 1168 The value is used to set the shell's compatibility level. 1169 See SHELL COMPATIBILITY MODE below for a description of the 1170 various compatibility levels and their effects. The value 1171 may be a decimal number (e.g., 4.2) or an integer (e.g., 42) 1172 corresponding to the desired compatibility level. If 1173 BASH_COMPAT is unset or set to the empty string, the 1174 compatibility level is set to the default for the current 1175 version. If BASH_COMPAT is set to a value that is not one of 1176 the valid compatibility levels, the shell prints an error 1177 message and sets the compatibility level to the default for 1178 the current version. The valid values correspond to the 1179 compatibility levels described below under SHELL 1180 COMPATIBILITY MODE. For example, 4.2 and 42 are valid values 1181 that correspond to the compat42 shopt option and set the 1182 compatibility level to 42. The current version is also a 1183 valid value. 4656 SHELL BUILTIN COMMANDS 6035 shopt [-pqsu] [-o] [optname ...] 6065 The list of shopt options is: 6112 compat31 6113 compat32 6114 compat40 6115 compat41 6116 compat42 6117 compat43 6118 compat44 6119 compat50 6120 These control aspects of the shell's compatibility 6121 mode (see SHELL COMPATIBILITY MODE below). 6679 SHELL COMPATIBILITY MODE 6708 Bash-4.3 introduced a new shell variable: BASH_COMPAT. The value 6709 assigned to this variable (a decimal version number like 4.2, or an 6710 integer corresponding to the compatNN option, like 42) determines 6711 the compatibility level. 6712 6713 Starting with bash-4.4, Bash has begun deprecating older 6714 compatibility levels. Eventually, the options will be removed in 6715 favor of BASH_COMPAT. 6716 6717 Bash-5.0 is the final version for which there will be an individual 6718 shopt option for the previous version. Users should use BASH_COMPAT 6719 on bash-5.0 and later versions. 6720 6721 The following table describes the behavior changes controlled by 6722 each compatibility level setting. The compatNN tag is used as 6723 shorthand for setting the compatibility level to NN using one of the 6724 following mechanisms. For versions prior to bash-5.0, the 6725 compatibility level may be set using the corresponding compatNN 6726 shopt option. For bash-4.3 and later versions, the BASH_COMPAT 6727 variable is preferred, and it is required for bash-5.1 and later 6728 versions. 6730 compat31 6734 compat32 6741 compat40 6749 compat41 6760 compat42 6772 compat43 6787 compat44 6801 compat50 6815 compat51
