printf_v format arg...
echo_v arg... echon_v arg...
print_v arg... print arg...
printf_v is like printf but output is produced only if VERBOSE is non-zero.
echo_v is like echo but output is produced only if VERBOSE is non-zero.
echon_v is like echo -n but output is produced only if VERBOSE is non-zero
print_v is like printf '%sn' but output is produced only if VERBOSE is non-zero
print is like printf '%sn'
return value is non-zero if VERBOSE is zero except for print.Otherwise, return value is the return status of printf