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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:\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 3.35 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://man7.org/linux/man-pages/.