Loop over tuples in bash?

bash for-loop
Frank picture Frank · Mar 15, 2012 · Viewed 53.6k times · Source

Is it possible to loop over tuples in bash?

As an example, it would be great if the following worked:

for (i,j) in ((c,3), (e,5)); do echo "$i and $j"; done

Is there a workaround that somehow lets me loop over tuples?

Answer

Eduardo Ivanec picture Eduardo Ivanec · Mar 15, 2012 
$ for i in c,3 e,5; do IFS=","; set -- $i; echo $1 and $2; done
c and 3
e and 5

About this use of set (from man builtins):

Any arguments remaining after option processing are treated as values for the positional parameters and are assigned, in order, to $1, $2, ... $n

The IFS="," sets the field separator so every $i gets segmented into $1 and $2 correctly.

Via this blog.

Edit: more correct version, as suggested by @SLACEDIAMOND:

$ OLDIFS=$IFS; IFS=','; for i in c,3 e,5; do set -- $i; echo $1 and $2; done; IFS=$OLDIFS
c and 3
e and 5

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