elf_cntl - control a file descriptor
cc [flag ...] file ... -lelf [library ...]
int elf_cntl(Elf *elf, Elf_Cmd cmd);
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
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.
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.
elf(3E), elf_begin(3E), elf_getdata(3E), elf_rawfile(3E).
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.
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