OK, so if you're here, you've probably been searching for a variable in mysqladmin and have watched twenty screens of spaces and pipes scroll past. Me too, so I'm just leaving this little snatch of formatting to remind myself how to tame it down to something readable. So if you're searching for 'buffer' related variables, you'll need something like this.
mysqladmin variables | tr -d " " | awk -F'|' '{print $2 " = " $3}' | grep buffer
Which gives you
aria_pagecache_buffer_size = 134217728 aria_sort_buffer_size = 268434432 bulk_insert_buffer_size = 16777216 innodb_buffer_pool_chunk_size = 134217728 innodb_buffer_pool_dump_at_shutdown = ON innodb_buffer_pool_dump_now = OFF innodb_buffer_pool_dump_pct = 25 innodb_buffer_pool_filename = ib_buffer_pool innodb_buffer_pool_instances = 1 innodb_buffer_pool_load_abort = OFF innodb_buffer_pool_load_at_startup = ON innodb_buffer_pool_load_now = OFF innodb_buffer_pool_size = 268435456 innodb_change_buffer_max_size = 25 innodb_change_buffering = all innodb_log_buffer_size = 8388608 innodb_sort_buffer_size = 1048576 join_buffer_size = 262144 join_buffer_space_limit = 2097152 key_buffer_size = 67108864 mrr_buffer_size = 262144 myisam_sort_buffer_size = 536870912 net_buffer_length = 16384 preload_buffer_size = 32768 read_buffer_size = 2097152 read_rnd_buffer_size = 1048576 sort_buffer_size = 4194304 sql_buffer_result = OFF
Alternatively, you might have some luck with
mysql -e "SHOW VARIABLES LIKE '%buffer%';"