arrays

To read the output of a command (naively) into an array:

$ grep iresome /usr/share/dict/words
tiresome
tiresomely
tiresomeness
tiresomeweed
# store the above list as an array
$ iresome=( $(grep iresome /usr/share/dict/words) )
# use declare -p to peek at the values in an array
$ declare -p iresome
declare -a iresome=([0]="tiresome" [1]="tiresomely" [2]="tiresomeness" [3]="tiresomeweed")

Simple! but doesn't work if they have spaces due to bash's always-infernal IFS

$ curl -s https://www.google.com | prettier --parser html | grep 'span>'
          ><span id="gbn" class="gbi"></span><span id="gbf" class="gbf"></span
                    type="submit" /></span></span
              ></span>
            /><span>Calling all young artists: Submit your artwork for </span
$ spans=( $(curl -s https://www.google.com | prettier --parser html | grep 'span>') )
$ declare -p spans
declare -a spans=([0]="><span" [1]="id=\"gbn\"" [2]="class=\"gbi\"></span><span" [3]="id=\"gbf\"" [4]="class=\"gbf\"></span" [5]="type=\"submit\"" [6]="/></span></span" [7]="></span>" [8]="/><span>Calling" [9]="all" [10]="young" [11]="artists:" [12]="Submit" [13]="your" [14]="artwork" [15]="for" [16]="</span")

We could fix this by changing IFS to just a newline, but then bash will still fail if the command substitution contains wildcards that match filenames.

Bash desperately wants to match file names, which is usually useful! but sometimes annoying.

The readarray builtin is the proper way to do this:

$ readarray -t spans < <(curl -s https://www.google.com | prettier --parser html | grep 'span>')
$ declare -p spans
declare -a spans=([0]="          ><span id=\"gbn\" class=\"gbi\"></span><span id=\"gbf\" class=\"gbf\"></span" [1]="                    type=\"submit\" /></span></span" [2]="              ></span>" [3]="            /><span>Calling all young artists: Submit your artwork for </span")

readarray is only available on bash >4, google up how to use read to do this on older bashes if you need that-t