Parsing ranges into discrete values, in Bash

Question

User will provide a list containing ranges. I need to convert it to a list of discrete values.

For example

Input

host[1-5],host7,host[13-15]

Output

host1,host2,host3,host4,host5,host7,host13,host14,host15.

How can I achieve this result?

Answer 1

Try this:

hosts=($(echo "host[1-5],host7,host[13-15]" | sed 's/,/ /g'))
string=""
for h in ${hosts[@]}; do 
  if [[ ! ${h//[^0-9]/} =~ ^[0-9]$ ]]; then
      for i in $(seq ${h//[^0-9]/ }); do 
        string+="${h%[*}$i,"
      done
  else
    string+="$h,"
  fi
done

echo "${string%,}"

Output:

host1,host2,host3,host4,host5,host7,host13,host14,host15,

Answer 2

Try bash's "Parameter expansion / pattern substitution"

$ hostlist=host[1-5],host7,host[13-15]
$ H1=${hostlist//[/{}
$ H2=${H1//]/\}}
$ H3=${H2//,/ }
$ H4=$(eval echo ${H3//-/..})
$ H5=${H4// /,}
$ echo "$H5"
host1,host2,host3,host4,host5,host7,host13,host14,host15

Answer 3

If you change your input to

hostlist=host{{1..5},7,{13..15}}

then

eval echo $hostlist | tr ' ' ,
host1,host2,host3,host4,host5,host7,host13,host14,host15