BashDB | A Key/Value store written entirely in bash | Script Programming library

According to Chet Ramey, shopt -s extdebug is internally equally to — debugger. And if bash doesn’t find a debugger during its initialization it unsets this option essentially making my return 1 useless. The above said only happens in non interactive mode since interactive shells can’t be debugged (hence the flags are not unset). And this explains clearly the behaviors stated in my question. So in scripts that should use my trap would need to reset shopt - s extdebug at the very top.

As Cyrus shows in his answer, a simplified version of your code - with the same input - does work on Linux in principle.

That said, your code references capture groups 3 and 4, whereas your regex only defines 2.

In other words: ${BASH_REMATCH[3]} and ${BASH_REMATCH[4]} are empty by definition.

Note, however, that if =~ signals success, BASH_REMATCH is never fully empty: at the very least - in the absence of any capture groups - ${BASH_REMATCH[0]} will be defined.

There are some general points worth making:

• Your shebang line reads #!/usr/bin/env /bin/bash, which is effectively the same as #!/bin/bash.

  • /usr/bin/env is typically used if you want a version other than /bin/bash to execute, one you've installed later and put in the PATH (too):
    #!/usr/bin/env bash

  • ghoti points out that another reason for using #!/usr/bin/env bash is to also support less common platforms such as FreeBSD, where bash, if installed, is located in /usr/local/bin rather than the usual /bin.

  • In either scenario it is less predictable which bash binary will be executed, because it depends on the effective $PATH value at the time of invocation.

• =~ is one of the few Bash features that are platform-dependent: it uses the particular regex dialect implemented by the platform's regex libraries.

  • \s is a character class shortcut that is not available on all platforms, notably not on macOS; the POSIX-compliant equivalent is [[:space:]].

  • (In your particular case, \s should work, however, because your Bash --version output suggests that you are on a Linux distro.)

• It's better not to use all-uppercase shell variable names such as INPUT, so as to avoid conflicts with environment variables and special shell variables.

history_lines_read_from_file belongs to file cygreadline7.dll that belongs to package libreadline7