extract characters between two commas?

Since cut prints non-delimited lines by default the following works

cut -f2 -d, file

awk -F, 'NF > 1 { $1 = $2 } { print $1 }' file

This uses awk to parse the file as lines consisting of comma-delimited fields.

The code detects when there is more than a single field on a line, and when there is, the first field is replaced by the second field. The first field, either unmodified or modified by the conditional code, is then printed.