HP-UX Reference (11i v1 05/09) - 3 Library Functions A-M (vol 6)

elf_begin(3E) elf_begin(3E)

if ((elf = elf_begin(fildes, ELF_C_WRITE, (Elf *)0)) == 0)

return;

ehdr = elf32_newehdr(elf);

phdr = elf32_newphdr(elf, count);

scn = elf_newscn(elf);

shdr = elf32_getshdr(scn);

data = elf_newdata(scn);

elf_update(elf, ELF_C_WRITE);

elf_end(elf);

Finally, the following outline shows how one might update an existing ELF ﬁle. Again, this example is

simpliﬁed to show the overall ﬂow.

elf_version(EV_CURRENT);

fildes = open("path/name", O_RDWR);

elf = elf_begin(fildes, ELF_C_RDWR, (Elf *)0);

/* add new or delete old information ...*/

close(creat("path/name", 0666));

elf_update(elf, ELF_C_WRITE);

elf_end(elf);

In the example above, the call to creat truncates the ﬁle, thus ensuring the resulting ﬁle will have the

‘‘right’’ size. Without truncation, the updated ﬁle might be as big as the original, even if information were

deleted. The library truncates the ﬁle, if it can, with ftruncate (see truncate(2)). Some systems, how-

ever, do not support

ftruncate, and the call to creat protects against this. Notice that both ﬁle crea-

tion examples open the ﬁle with write and read permissions. On systems that support mmap, the library

uses it to enhance performance, and

mmap requires a readable ﬁle descriptor. Although the library can use

a write-only ﬁle descriptor, the application will not obtain the performance advantages of mmap.