executing variable substitution/String manipultion N times-CodePudding

But methods in that question are not working for variable assignments

Eg.

var='abc,xyz,mnx,duid'
for f in `seq 3`; do var=${var%,*}; done

Above works but using it in function as described in other question does't work

Eg.

repeat() { num="$"; shift; for f in $(seq $num); do $1; done; }
repeat 3 'var=${var%,*}'
repeat 3 "var=${var%,*}"

Doesn't work

CodePudding user response：

Variable expansions and assignments aren't processed after expanding variables. You need to use eval to re-execute it as a shell command.

You also have a typo, "$" should be "$1".

repeat() { num="$1"; shift; for f in $(seq $num); do eval "$1"; done; }
repeat 3 'var=${var%,*}'
echo "$var" # output = abc

Note that the argument needs to be in single quotes, otherwise the variable expansion will be processed once before calling the function.

CodePudding user response：

Based on your sample data

var='abc,xyz,mnx,duid'

you can also have the same effect by concatenating the search terms multiple times

var=${var%,*,*,*}

That said, you could also do things like

var=${var%$(printf ',*%.0s' {1..3})}

n=3; var=${var%$(printf ',*%.0s' $(seq $n))}