ISBLANK (man3p)
isblank, isblank_l — test for a blank character
isblank, isblank_l — test for a blank character
if_nameindex — return all network interface names and indexes
wcsrchr — wide-character string scanning operation
strtod, strtof, strtold — convert a string to a double-precision number
sem_wait — lock a semaphore
funlockfile — stdio locking functions
shmat — XSI shared memory attach operation
pthread_equal — compare thread IDs
csin, csinf, csinl — complex sine functions
strdup, strndup — duplicate a specific number of bytes from a string