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).

STANDARDS

       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(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);
       }

SEE ALSO

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