I create an array with a comma for delimiter:
echo "${myarray[*]}" # prints: 22,3,2,0,22,4,5,8,22,4,3,6 I'd like to print it to terminal in chunks of four, with a newline and no comma before newline. Like:
22,3,2,0 22,4,5,8 22,4,3,6 I've been struggling trying to get for loops to work with it like:
for i in {0..${#myarray[@]}..4} do ##tried lots of things that didn't work here done Can someone point me in the right direction or how to think about it?
If the number of elements is guaranteed to be a multiple of 4 and greater than 0:
$ myarray=(22 3 2 0 22 4 5 8 22 4 3 6) $ printf '%s,%s,%s,%s\n' "${myarray[@]}" 22,3,2,0 22,4,5,8 22,4,3,6 If not, that gives:
$ myarray=(22 3 2 0 22 4 5 8 22 4 3 6 extra) $ printf '%s,%s,%s,%s\n' "${myarray[@]}" 22,3,2,0 22,4,5,8 22,4,3,6 extra,,, $ myarray=() $ printf '%s,%s,%s,%s\n' "${myarray[@]}" ,,, With zsh:
myarray=(22 3 2 0 22 4 5 8 22 4 3 6 extra) while (( $#myarray )) { print -r -- ${(j[,])myarray[1,4]} myarray[1,4]=() } Which modifies $myarray or:
myarray=(22 3 2 0 22 4 5 8 22 4 3 6 extra) for (( i = 1; i <= $#myarray; i += 4 )) print -r -- ${(j[,])myarray[i,i+3]} Which both give:
22,3,2,0 22,4,5,8 22,4,3,6 extra That latter one you could do in bash with:
myarray=(22 3 2 0 22 4 5 8 22 4 3 6 extra) (IFS=, for (( i = 0; i < ${#myarray[@]}; i += 4 )) { printf '%s\n' "${myarray[*]:i:4}" } ) Relying on "${array[*]}" to join the elements with the first character of $IFS as bash has no equivalent for zsh's join parameter expansion flag.
$ printf '%s\n' "${myarray[@]}" | paste -d , - - - - 22,3,2,0 22,4,5,8 22,4,3,6 This uses printf to produce one line of input to paste per element in your array. The paste utility distributes these lines over four comma-delimited fields per output line.
There is no need for a separate loop in the shell.
Whatever is producing your array's elements could replace the printf call, and you could, that way, bypass creating the array completely.
some-command | paste -d , - - - - Note that some-command can be an arbitrarily complex compound command.
printf call, only passed on by it. But I definitely see what you're saying. Such newlines would mess up the paste processing.How about this:
#!/usr/bin/env bash myarray=(22 3 2 0 22 4 5 8 22 4 3 6) for ((i=0; i<"${#myarray[@]}"; i+=4)); do echo "${myarray[$i]},${myarray[$i+1]},${myarray[$i+2]},${myarray[$i+3]}" done 
22, and you have that data in some textfile or similar, there are simpler ways (e.g. tr, grep, sed, awk, ...) to get this output than loading them into a bash array.reads and that number will change. thanks so much. (i couldnt figure how to iterate by 4 with that syntax... so i def learned something)CommentedAug 9, 2024 at 5:42echo "${myarray[*]:i:4}" with IFS=, instead of manually listing them. Though modifying IFS has a global effect, but then the original question used "${myarray[*]}" too.$ in an arithmetic expression: echo "${myarray[i]},${myarray[i+1]},${myarray[i+2]},${myarray[i+3]}"CommentedAug 9, 2024 at 13:36
{0..$n..4}is not recognized as a brace expansion, and left as-is, and then after variable expansion it gives you{0..123..4}, so nothing you do inside the loop really matters.echo "${myarray[*]}"indicatesmyarrayis not an array but rather a single string; please update the question with the complete output fromtypeset -p myarray