elf_cntl(3E)

NAME
     elf_cntl - control a file descriptor

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

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

DESCRIPTION
     elf_cntl instructs the library to modify its behavior with respect to an
     ELF descriptor, elf.  As elf_begin(3E) describes, an ELF descriptor can
     have multiple activations, and multiple ELF descriptors may share a
     single file descriptor.  Generally, elf_cntl 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.

     ELF_C_FDDONE
               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 elf_getdata for a section, will
               fail if the data are not in memory already.

     ELF_C_FDREAD
               This command is similar to ELF_C_FDDONE, 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 elf_cntl
               completes the ELF_C_FDREAD command, future operations, such as
               elf_getdata, will use the memory version of the file without
               needing to use the file descriptor.

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

SEE ALSO
     elf(3E), elf_begin(3E), elf_getdata(3E), elf_rawfile(3E).

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