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NAME | SYNOPSIS | DESCRIPTION | STANDARDS | HISTORY | NOTES | EXAMPLES | SEE ALSO | COLOPHON |
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end(3) Library Functions Manual end(3)
etext, edata, end - end of program segments
extern etext;
extern edata;
extern end;
The addresses of these symbols indicate the end of various
program segments:
etext This is the first address past the end of the text segment
(the program code).
edata This is the first address past the end of the initialized
data segment.
end This is the first address past the end of the
uninitialized data segment (also known as the BSS
segment).
None.
Although these symbols have long been provided on most UNIX
systems, they are not standardized; use with caution.
The program must explicitly declare these symbols; they are not
defined in any header file.
On some systems the names of these symbols are preceded by
underscores, thus: _etext, _edata, and _end. These symbols are
also defined for programs compiled on Linux.
At the start of program execution, the program break will be
somewhere near &end (perhaps at the start of the following page).
However, the break will change as memory is allocated via brk(2)
or malloc(3). Use sbrk(2) with an argument of zero to find the
current value of the program break.
When run, the program below produces output such as the
following:
$ ./a.out
First address past:
program text (etext) 0x8048568
initialized data (edata) 0x804a01c
uninitialized data (end) 0x804a024
Program source
#include <stdio.h>
#include <stdlib.h>
extern char etext, edata, end; /* The symbols must have some type,
or "gcc -Wall" complains */
int
main(void)
{
printf("First address past:\n");
printf(" program text (etext) %10p\n", &etext);
printf(" initialized data (edata) %10p\n", &edata);
printf(" uninitialized data (end) %10p\n", &end);
exit(EXIT_SUCCESS);
}
objdump(1), readelf(1), sbrk(2), elf(5)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.9.1.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.9.1 2024-06-15 end(3)
Pages that refer to this page: brk(2)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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