i386_set_ldt(2) [freebsd man page]

I386_GET_LDT(2) 					      BSD System Calls Manual						   I386_GET_LDT(2)

NAME

     i386_get_ldt, i386_set_ldt -- manage i386 per-process Local Descriptor Table entries

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <machine/segments.h>
     #include <machine/sysarch.h>

     int
     i386_get_ldt(int start_sel, union descriptor *descs, int num_sels);

     int
     i386_set_ldt(int start_sel, union descriptor *descs, int num_sels);

DESCRIPTION

     The i386_get_ldt() system call returns a list of the i386 descriptors in the current process' LDT.  The i386_set_ldt() system call sets a
     list of i386 descriptors in the current process' LDT.  For both routines, start_sel specifies the index of the selector in the LDT at which
     to begin and descs points to an array of num_sels descriptors to be set or returned.

     Each entry in the descs array can be either a segment_descriptor or gate_descriptor and are defined in <i386/segments.h>.	These structures
     are defined by the architecture as disjoint bit-fields, so care must be taken in constructing them.

     If start_sel is LDT_AUTO_ALLOC, num_sels is 1 and the descriptor pointed to by descs is legal, then i386_set_ldt() will allocate a descriptor
     and return its selector number.

     If num_descs is 1, start_sels is valid, and descs is NULL, then i386_set_ldt() will free that descriptor (making it available to be reallo-
     cated again later).

     If num_descs is 0, start_sels is 0 and descs is NULL then, as a special case, i386_set_ldt() will free all descriptors.

RETURN VALUES

     Upon successful completion, i386_get_ldt() returns the number of descriptors currently in the LDT.  The i386_set_ldt() system call returns
     the first selector set on success.  If the kernel allocated a descriptor in the LDT, the allocated index is returned.  Otherwise, a value of
     -1 is returned and the global variable errno is set to indicate the error.

ERRORS

     The i386_get_ldt() and i386_set_ldt() system calls will fail if:

     [EINVAL]		An inappropriate value was used for start_sel or num_sels.

     [EACCES]		The caller attempted to use a descriptor that would circumvent protection or cause a failure.

SEE ALSO

     i386 Microprocessor Programmer's Reference Manual, Intel

WARNING

     You can really hose your process using this.

BSD
								 October 14, 2006							       BSD

CLOSE(2)						      BSD System Calls Manual							  CLOSE(2)

NAME

     close -- delete a descriptor

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <unistd.h>

     int
     close(int fd);

DESCRIPTION

     The close() system call deletes a descriptor from the per-process object reference table.	If this is the last reference to the underlying
     object, the object will be deactivated.  For example, on the last close of a file the current seek pointer associated with the file is lost;
     on the last close of a socket(2) associated naming information and queued data are discarded; on the last close of a file holding an advisory
     lock the lock is released (see further flock(2)).	However, the semantics of System V and IEEE Std 1003.1-1988 (``POSIX.1'') dictate that all
     fcntl(2) advisory record locks associated with a file for a given process are removed when any file descriptor for that file is closed by
     that process.

     When a process exits, all associated file descriptors are freed, but since there is a limit on active descriptors per processes, the close()
     system call is useful when a large quantity of file descriptors are being handled.

     When a process forks (see fork(2)), all descriptors for the new child process reference the same objects as they did in the parent before the
     fork.  If a new process is then to be run using execve(2), the process would normally inherit these descriptors.  Most of the descriptors can
     be rearranged with dup2(2) or deleted with close() before the execve(2) is attempted, but if some of these descriptors will still be needed
     if the execve fails, it is necessary to arrange for them to be closed if the execve succeeds.  For this reason, the call ``fcntl(d, F_SETFD,
     FD_CLOEXEC)'' is provided, which arranges that a descriptor will be closed after a successful execve; the call ``fcntl(d, F_SETFD, 0)''
     restores the default, which is to not close the descriptor.

RETURN VALUES

     The close() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate
     the error.

ERRORS

     The close() system call will fail if:

     [EBADF]		The fd argument is not an active descriptor.

     [EINTR]		An interrupt was received.

     [ENOSPC]		The underlying object did not fit, cached data was lost.

     [ECONNRESET]	The underlying object was a stream socket that was shut down by the peer before all pending data was delivered.

     In case of any error except EBADF, the supplied file descriptor is deallocated and therefore is no longer valid.

SEE ALSO

     accept(2), closefrom(2), execve(2), fcntl(2), flock(2), open(2), pipe(2), socket(2), socketpair(2)

STANDARDS

     The close() system call is expected to conform to ISO/IEC 9945-1:1990 (``POSIX.1'').

HISTORY

     The close() function appeared in Version 7 AT&T UNIX.

BSD
								September 11, 2013							       BSD