Add text to SYNOPSIS noting the need to link with "-lrt" or "-pthread".

man3/sem_close.3

@@ -29,6 +29,8 @@ sem_close \- close a named semaphore
 .sp
 .BI "int sem_close(sem_t *" sem );
 .fi
+.sp
+Link with \fI\-lrt\fP or \fI\-pthread\fP.
 .SH DESCRIPTION
 .BR sem_close ()
 closes the named semaphore referred to by

man3/sem_destroy.3

@@ -29,6 +29,8 @@ sem_destroy \- destroy an unnamed semaphore
 .sp
 .BI "int sem_destroy(sem_t *" sem );
 .fi
+.sp
+Link with \fI\-lrt\fP or \fI\-pthread\fP.
 .SH DESCRIPTION
 .BR sem_destroy ()
 destroys the unnamed semaphore at the address pointed to by

man3/sem_getvalue.3

@@ -29,6 +29,8 @@ sem_getvalue \- get the value of a semaphore
 .sp
 .BI "int sem_getvalue(sem_t *" sem ", int *" sval );
 .fi
+.sp
+Link with \fI\-lrt\fP or \fI\-pthread\fP.
 .SH DESCRIPTION
 .BR sem_getvalue ()
 places the current value of the semaphore pointed to

man3/sem_init.3

@@ -29,6 +29,8 @@ sem_init \- initialize an unnamed semaphore
 .sp
 .BI "int sem_init(sem_t *" sem ", int " pshared ", unsigned int " value );
 .fi
+.sp
+Link with \fI\-lrt\fP or \fI\-pthread\fP.
 .SH DESCRIPTION
 .BR sem_init ()
 initializes the unnamed semaphore at the address pointed to by

man3/sem_open.3

@@ -31,6 +31,8 @@ sem_open \- initialize and open a named semaphore
 .BI "sem_t *sem_open(const char *" name ", int " oflag ", "
 .BI "                mode_t " mode ", unsigned int " value );
 .fi
+.sp
+Link with \fI\-lrt\fP or \fI\-pthread\fP.
 .SH DESCRIPTION
 .BR sem_open ()
 creates a new POSIX semaphore or opens an existing semaphore.

man3/sem_post.3

@@ -29,6 +29,8 @@ sem_post \- unlock a semaphore
 .sp
 .BI "int sem_post(sem_t *" sem );
 .fi
+.sp
+Link with \fI\-lrt\fP or \fI\-pthread\fP.
 .SH DESCRIPTION
 .BR sem_post ()
 increments (unlocks) the semaphore pointed to by

man3/sem_unlink.3

@@ -29,6 +29,8 @@ sem_unlink \- remove a named semaphore
 .sp
 .BI "int sem_unlink(const char *" name );
 .fi
+.sp
+Link with \fI\-lrt\fP or \fI\-pthread\fP.
 .SH DESCRIPTION
 .BR sem_unlink ()
 removes the named semaphore referred to by

man3/sem_wait.3

@@ -34,6 +34,8 @@ sem_wait, sem_timedwait, sem_trywait \- lock a semaphore
 .BI "int sem_timedwait(sem_t *" sem ", const struct timespec *" abs_timeout );
 .fi
 .sp
+Link with \fI\-lrt\fP or \fI\-pthread\fP.
+.sp
 .in -4n
 Feature Test Macro Requirements for glibc (see
 .BR feature_test_macros (7)):