MQ_UNLINK (man3p)
mq_unlink — remove a message queue (REALTIME)
mq_unlink — remove a message queue (REALTIME)
getpgrp — get the process group ID of the calling process
putchar_unlocked — stdio with explicit client locking
mq_send, mq_timedsend — send a message to a message queue (REALTIME)
setservent — network services database functions
setregid — set real and effective group IDs
posix_spawnattr_getsigmask, posix_spawnattr_setsigmask — get and set the spawn-sigmask attribute of a spawn attributes object (ADVANCED REALTIME)
ccosh, ccoshf, ccoshl — complex hyperbolic cosine functions
dirname — report the parent directory name of a file pathname
tolower, tolower_l — transliterate uppercase characters to lowercase