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with-lower-version-bash.md

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With Bash version < 4.4

If you want use Lobash with Bash 4.3 and lower versions, there are some knowledges you should know.

Compatible with different Bash versions

This section only show the compatibilities with different Bash versions.

There is a list of which features were added to specific releases (versions) of Bash.

4.4

Completely supported.

4.3

  • shopt -s inherit_errexit is a new feature in Bash v4.4. There is no workaround in v4.3.
  • declare -p has a bug. See ./module-usages/condition.md#is_array and ./module-usages/condition.md#is_exported.
    • You should always declare a variable with initialization, like declare -a var=(), local var=, export var= instead of declare -a var, local var, export var.
  • Only with bash 4.3, when declare -a a, the declare -p a shows declare: a: not found.
  • readarray: -d: invalid option util 4.4.

4.2

  • The Nameref is new feature in Bash v4.3. Use eval as workaround.
  • declare -p has a bug. See ./module-usages/condition.md#is_exported.
    • You should always declare a variable with initialization, like declare -a var=(), local var=, export var= instead of declare -a var, local var, export var.
  • readarray: -d: invalid option util 4.4.
  • For associative array, [[ -v array[key] ]] and test -v array[key] always be 1 util 4.3.

4.1

  • declare -g var=str not supported util v4.2, use read -r var <<< "str" instead.
  • $(( "$i" + 1 )) not work in Bash 4.1, use $(( i + 1)) instead.
  • [[ $'\e' == $'\u001b' ]] is false in Bash less than v4.2. No workaround.
  • printf "%($1)T\\n" "-1" not work in v4.1. No workaround.
  • declare -p has a bug. See ./module-usages/condition.md#is_exported.
    • You should always declare a variable with initialization, like declare -a var=(), local var=, export var= instead of declare -a var, local var, export var.
  • readarray: -d: invalid option util 4.4.
  • For associative array, [[ -v array[key] ]] and test -v array[key] always be 1 util 4.3.

4.0

  • exec {_sleep_fd}<> <(true) is not supported util v4.1. No workaround.

  • declare -p has a bug. See ./module-usages/condition.md#is_exported.

    • You should always declare a variable with initialization, like declare -a var=(), local var=, export var= instead of declare -a var, local var, export var.

  • readarray: -d: invalid option util 4.4.

  • For associative array, [[ -v array[key] ]] and test -v array[key] always be 1 util 4.3.

  • Empty $@ and $* will throw error "unbound variable" with set -u in v4.0. It is a bug of Bash. See https://unix.stackexchange.com/a/16565

Not test with Bash 4.0

Lobash not test with Bash 4.0 in MacOS and Linux. It seems a bug of Bash 4.0. Please contact me if you solved this problem.

To reproduce the problem for Linux,

# For Linux
> BASHVER=4.0 ./tools/test

malloc: hashlib.c:306: assertion botched
free: called with unallocated block argument

To reproduce the problem for MacOS,

# For MacOS
> BASHVER=4.0 ./tools/test
bash(38696,0x7fff989c2380) malloc: *** error for object 0x1061ad800: pointer being freed was not allocated

What you should do with Lobash in different Bash versions

Lobash will not include modules whose metadata Bash higher than target Bash version when build.

You can implement similar functions by reading Lobash source codes as references.

4.4

Nothing else.

4.3

Because there is no workaround and similar mechanism for fast-failing (inherit_errexit), it is your responsibility to keep the program always on right processing. Test your script with complete boundary testings. Make sure your script never get unexpected trapped.

Still add this line (shopt -p inherit_errexit &>/dev/null) && shopt -s inherit_errexit to your script to keep compatible with higher versions.

4.2

Same to 4.3.

4.1

Same to 4.3.

4.0

Same to 4.3.