END(3) Linux Programmer's Manual END(3)
etext, edata, end - end of program segments
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).
Although these symbols have long been provided on most UNIX systems, they are not stan-
dardized; use with caution.
The program must explicitly declare these symbols; they are not defined in any header
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 allo-
cated 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:
First address past:
program text (etext) 0x8048568
initialized data (edata) 0x804a01c
uninitialized data (end) 0x804a024
extern char etext, edata, end; /* The symbols must have some type,
or "gcc -Wall" complains */
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);
objdump(1), readelf(1), sbrk(2), elf(5)
This page is part of release 3.53 of the Linux man-pages project. A description of the
project, and information about reporting bugs, can be found at
GNU 2008-07-17 END(3)