Suppress emission of delimiter after final PID when using pgrep's -d switch

[lstewart]

Summary

pgrep naively appends the delimiter to all PIDs including the last. e.g. "pgrep -d, getty" outputs "1399,1386,1309,1308,1307,1306,1305,1302,"
Ensure the list is correctly delimited by suppressing the emission of the delimiter after the final PID.

Sponsored by: Netflix, Inc.

[imp]

Lots of ways to skin this cat, this is as good as any other.

[kib]

We have working C99 bool type.

[lstewart]

@kib: You prefer this?

[kib]

As a very minimal start, yes. You may consider changing the return type of action to bool and do the necessary cascade of related changes.