exec - execute commands in the operating system shell

yosys> help exec

exec [options] -- [command]

Execute a command in the operating system shell.  All supplied arguments are
concatenated and passed as a command to popen(3).  Whitespace is not guaranteed
to be preserved, even if quoted.  stdin and stderr are not connected, while
stdout is logged unless the "-q" option is specified.

-q

Suppress stdout and stderr from subprocess

-expect-return <int>

Generate an error if popen() does not return specified value.
May only be specified once; the final specified value is controlling
if specified multiple times.

-expect-stdout <regex>

Generate an error if the specified regex does not match any line
in subprocess's stdout.  May be specified multiple times.

-not-expect-stdout <regex>

Generate an error if the specified regex matches any line
in subprocess's stdout.  May be specified multiple times.

Example: exec -q -expect-return 0 -- echo "bananapie" | grep "nana"