Where Online Learning is simpler!

The C and C++ Include Header Files

/usr/include/x86_64-linux-gnu/bits/unistd_ext.h


$ cat -n /usr/include/x86_64-linux-gnu/bits/unistd_ext.h

     1	/* System-specific extensions of <unistd.h>, Linux version.
     2	   Copyright (C) 2019-2024 Free Software Foundation, Inc.
     3	   This file is part of the GNU C Library.
     4	
     5	   The GNU C Library is free software; you can redistribute it and/or
     6	   modify it under the terms of the GNU Lesser General Public
     7	   License as published by the Free Software Foundation; either
     8	   version 2.1 of the License, or (at your option) any later version.
     9	
    10	   The GNU C Library is distributed in the hope that it will be useful,
    11	   but WITHOUT ANY WARRANTY; without even the implied warranty of
    12	   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    13	   Lesser General Public License for more details.
    14	
    15	   You should have received a copy of the GNU Lesser General Public
    16	   License along with the GNU C Library; if not, see
    17	   <https://www.gnu.org/licenses/>.  */
    18	
    19	#ifndef _UNISTD_H
    20	# error "Never include <bits/unistd_ext.h> directly; use <unistd.h> instead."
    21	#endif
    22	
    23	#ifdef __USE_GNU
    24	
    25	/* Return the kernel thread ID (TID) of the current thread.  The
    26	   returned value is not subject to caching.  Most Linux system calls
    27	   accept a TID in place of a PID.  Using the TID to change properties
    28	   of a thread that has been created using pthread_create can lead to
    29	   undefined behavior (comparable to manipulating file descriptors
    30	   directly that have not been created explicitly).  Note that a TID
    31	   uniquely identifies a thread only while this thread is running; a
    32	   TID can be reused once a thread has exited, even if the thread is
    33	   not detached and has not been joined.  */
    34	extern __pid_t gettid (void) __THROW;
    35	
    36	#ifdef __has_include
    37	# if __has_include ("linux/close_range.h")
    38	#  include "linux/close_range.h"
    39	# endif
    40	#endif
    41	/* Unshare the file descriptor table before closing file descriptors.  */
    42	#ifndef CLOSE_RANGE_UNSHARE
    43	# define CLOSE_RANGE_UNSHARE (1U << 1)
    44	#endif
    45	/* Set the FD_CLOEXEC bit instead of closing the file descriptor.  */
    46	#ifndef CLOSE_RANGE_CLOEXEC
    47	# define CLOSE_RANGE_CLOEXEC (1U << 2)
    48	#endif
    49	
    50	#endif /* __USE_GNU  */