cc -pthread  -Wall -Wextra -Werror=implicit-function-declaration unistd/lockf.c -o unistd/lockf -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE -lm -lpthread -lrt -lintl -liconv
unistd/lockf.c: In function ‘main’:
unistd/lockf.c:17:14: error: implicit declaration of function ‘lockf’ [-Wimplicit-function-declaration]
   17 |         if ( lockf(fd, F_LOCK, 0) < 0 )
      |              ^~~~~
unistd/lockf.c:17:24: error: ‘F_LOCK’ undeclared (first use in this function); did you mean ‘F_OK’?
   17 |         if ( lockf(fd, F_LOCK, 0) < 0 )
      |                        ^~~~~~
      |                        F_OK
unistd/lockf.c:17:24: note: each undeclared identifier is reported only once for each function it appears in
unistd/lockf.c:26:32: error: ‘F_TLOCK’ undeclared (first use in this function); did you mean ‘F_OK’?
   26 |                 if ( lockf(fd, F_TLOCK, 0) < 0 )
      |                                ^~~~~~~
      |                                F_OK