The C and C++ Include Header Files

/usr/include/errno.h


$ cat -n /usr/include/errno.h

     1	/* Copyright (C) 1991-2024 Free Software Foundation, Inc.
     2	   This file is part of the GNU C Library.
     3	
     4	   The GNU C Library is free software; you can redistribute it and/or
     5	   modify it under the terms of the GNU Lesser General Public
     6	   License as published by the Free Software Foundation; either
     7	   version 2.1 of the License, or (at your option) any later version.
     8	
     9	   The GNU C Library is distributed in the hope that it will be useful,
    10	   but WITHOUT ANY WARRANTY; without even the implied warranty of
    11	   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    12	   Lesser General Public License for more details.
    13	
    14	   You should have received a copy of the GNU Lesser General Public
    15	   License along with the GNU C Library; if not, see
    16	   <https://www.gnu.org/licenses/>.  */
    17	
    18	/*
    19	 *	ISO C99 Standard: 7.5 Errors	<errno.h>
    20	 */
    21	
    22	#ifndef	_ERRNO_H
    23	#define	_ERRNO_H 1
    24	
    25	#include <features.h>
    26	
    27	/* The system-specific definitions of the E* constants, as macros.  */
    28	#include <bits/errno.h>
    29	
    30	/* When included from assembly language, this header only provides the
    31	   E* constants.  */
    32	#ifndef __ASSEMBLER__
    33	
    34	__BEGIN_DECLS
    35	
    36	/* The error code set by various library functions.  */
    37	extern int *__errno_location (void) __THROW __attribute_const__;
    38	# define errno (*__errno_location ())
    39	
    40	# ifdef __USE_GNU
    41	
    42	/* The full and simple forms of the name with which the program was
    43	   invoked.  These variables are set up automatically at startup based on
    44	   the value of argv[0].  */
    45	extern char *program_invocation_name;
    46	extern char *program_invocation_short_name;
    47	
    48	#include <bits/types/error_t.h>
    49	
    50	# endif /* __USE_GNU */
    51	
    52	__END_DECLS
    53	
    54	#endif /* !__ASSEMBLER__ */
    55	#endif /* errno.h */