END(3)                                                       Linux Programmer's Manual                                                      END(3)

NAME

       etext, edata, end - end of program segments

SYNOPSIS

       extern etext;
       extern edata;
       extern end;

DESCRIPTION

       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).

CONFORMING TO

       Although these symbols have long been provided on most UNIX systems, they are not standardized; use with caution.

NOTES

       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.

EXAMPLE

       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(int argc, char *argv[])
       {
           printf("First address past:
");
           printf("    program text (etext)      %10p
", &etext);
           printf("    initialized data (edata)  %10p
", &edata);
           printf("    uninitialized data (end)  %10p
", &end);

           exit(EXIT_SUCCESS);
       }

SEE ALSO

       objdump(1), readelf(1), sbrk(2), elf(5)

COLOPHON

       This page is part of release 4.15 of the Linux man-pages project.  A description of the project, information about reporting bugs, and  the
       latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

GNU                                                                 2017-09-15                                                              END(3)