elf_cntl(3E)                   (ELF Library)                   elf_cntl(3E)


   NAME
         elfcntl - control a file descriptor

   SYNOPSIS
         cc [flag ...] file ...  -lelf [library ...]

         #include <libelf.h>
         int elfcntl(Elf *elf, ElfCmd cmd);

   DESCRIPTION
         elfcntl instructs the library to modify its behavior with respect to
         an ELF descriptor, elf.  As elfbegin(3E) describes, an ELF
         descriptor can have multiple activations, and multiple ELF
         descriptors may share a single file descriptor.  Generally, elfcntl
         commands apply to all activations of elf.  Moreover, if the ELF
         descriptor is associated with an archive file, descriptors for
         members within the archive will also be affected as described below.
         Unless stated otherwise, operations on archive members do not affect
         the descriptor for the containing archive.

         The cmd argument tells what actions to take and may have the
         following values.

         ELFCFDDONE
                   This value tells the library not to use the file descriptor
                   associated with elf.  A program should use this command
                   when it has requested all the information it cares to use
                   and wishes to avoid the overhead of reading the rest of the
                   file.  The memory for all completed operations remains
                   valid, but later file operations, such as the initial
                   elfgetdata for a section, will fail if the data are not in
                   memory already.

         ELFCFDREAD
                   This command is similar to ELFCFDDONE, except it forces
                   the library to read the rest of the file.  A program should
                   use this command when it must close the file descriptor but
                   has not yet read everything it needs from the file.  After
                   elfcntl completes the ELFCFDREAD command, future
                   operations, such as elfgetdata, will use the memory
                   version of the file without needing to use the file
                   descriptor.

         If elfcntl succeeds, it returns zero.  Otherwise elf was null or an
         error occurred, and the function returns -1.

   SEE ALSO
         elf(3E), elfbegin(3E), elfgetdata(3E), elfrawfile(3E).





   8/91                                                                 Page 1

   elf_cntl(3E)                   (ELF Library)                   elf_cntl(3E)


   NOTE
         If the program wishes to use the ``raw'' operations [see elfrawdata,
         which elfgetdata(3E) describes, and elfrawfile(3E)] after disabling
         the file descriptor with ELFCFDDONE or ELFCFDREAD, it must
         execute the raw operations explicitly beforehand.  Otherwise, the raw
         file operations will fail.  Calling elfrawfile makes the entire
         image available, thus supporting subsequent elfrawdata calls.














































   Page 2                                                                 8/91