elf_cntl(3E)                                                   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 descrip-
     tor 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 associ-
     ated 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 asso-
          ciated 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 is 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() com-
          pletes 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.

NOTES
     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.



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elf_cntl(3E)                                                   elf_cntl(3E)

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




















































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