On Tue, Feb 03, 2026 at 01:19:35 +0000, [email protected] wrote:
> On Mon, 2 Feb 2026, Greg Wooledge wrote:
>
> > On Mon, Feb 02, 2026 at 23:30:16 +0000, [email protected] wrote:
> >> don't know what he meant
> >> https://stackoverflow.com/questions/7578930/bash-split-string-into-character-array
> >
> > Oh, so you didn't actually WRITE the code.
> >
> > Was your question "How does this code work?"
>
> yes
OK, here's the code once again:
string='whatever'
[[ $string =~ ${string//?/(.)} ]]
array=( "${BASH_REMATCH[@]:1}" )
The first line is just assigning the input, which in a real script
would come from somewhere other than the script itself.
The second line is really doing two things. It's been written as a
single line for brevity. Let's break it apart:
re=${string//?/(.)}
[[ $string =~ $re ]]
I've inserted the temporary variable "re" here, to hold a regular
expression. This is the real magic. "re" contains a regexp which
has one instance of "(.)" for every character in the input string.
For example, if the input string has 8 characters, the re has 24.
hobbit:~$ string='whatever'
hobbit:~$ re=${string//?/(.)}
hobbit:~$ declare -p re
declare -- re="(.)(.)(.)(.)(.)(.)(.)(.)"
The [[ command with =~ operator matches a string (the left hand side)
against an Extended Regular Expression (the right hand side).
[[ $string =~ $re ]]
expands to
[[ whatever =~ (.)(.)(.)(.)(.)(.)(.)(.) ]]
Each (.) is a single-character wildcard match with parentheses around it,
meaning it's captured as a substring. The first (.) captures the w,
the second captures the h, the third captures the a, and so on.
After a [[ command with =~ operator has completed, the BASH_REMATCH
array will be populated with the substring that matched the full
regular expression (index 0), and then each captured substring
(index 1 and beyond).
hobbit:~$ [[ $string =~ $re ]]
hobbit:~$ declare -p BASH_REMATCH
declare -a BASH_REMATCH=([0]="whatever" [1]="w" [2]="h" [3]="a" [4]="t"
[5]="e" [6]="v" [7]="e" [8]="r")
Finally, we have
array=( "${BASH_REMATCH[@]:1}" )
which simply copies the elements of the BASH_REMATCH array starting
at index 1 into the output array variable.
hobbit:~$ array=( "${BASH_REMATCH[@]:1}" )
hobbit:~$ declare -p array
declare -a array=([0]="w" [1]="h" [2]="a" [3]="t" [4]="e" [5]="v" [6]="e"
[7]="r")
