end

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.

EXAMPLES
       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:\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);
       }

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

COLOPHON
       This page is part of release 5.13 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                                2020-06-09                             END(3)