ctermid
(3)get controlling terminal name
#include <stdio.h> char *ctermid(char *s); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): ctermid(): _POSIX_C_SOURCE
LIBRARY
DESCRIPTION
ctermid() returns a string which is the pathname for the current controlling terminal for this process. If s is NULL, a static buffer is used, otherwise s points to a buffer used to hold the terminal pathname. The symbolic constant L_ctermid is the maximum number of characters in the returned pathname.