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NAME

elf_begin

 - open an ELF file or ar(1) archive

 

LIBRARY

Lb libelf

 

SYNOPSIS

DESCRIPTION

Argument fd is an open file descriptor returned from an open(2) system call. Function elf_begin ();
uses argument fd for reading or writing depending on the value of argument cmd Argument elf is primarily used for iterating through archives.

The argument cmd can have the following values:

ELF_C_NULL

Causes elf_begin ();
to return NULL. Arguments fd and elf are ignored, and no additional error is signalled.

ELF_C_READ

This value is to be when the application wishes to examine (but not modify) the contents of the file specified by argument fd It can be used for both ar(1) archives and for regular ELF files.

Argument fd should have been opened for reading. If argument elf is NULL, the library will allocate a new ELF descriptor for the file being processed. If argument elf is not NULL, and references a regular ELF file previously opened with elf_begin (,);
then the activation count for elf is incremented. If argument elf is not NULL, and references a descriptor for an ar(1) archive opened earlier with elf_begin (,);
a descriptor for an element in the archive is returned as described in the section Sx Processing ar(1) archives below.

ELF_C_RDWR

The command is used to prepare an ELF file for reading and writing. It is not supported for archives.

Argument fd should have been opened for reading and writing. If argument elf is NULL, the library will allocate a new ELF descriptor for the file being processed. If the argument elf is non-null, it should point to a descriptor previously allocated with elf_begin ();
with the same values for arguments fd and cmd in this case the library will increment the activation count for descriptor elf and return the same descriptor. Changes to the in-memory image of the ELF file are written back to disk using the elf_update3 function.

This command is not valid for ar(1) archives.

ELF_C_WRITE

This command is used when the application wishes to create a new ELF file. Argument fd should have been opened for writing. Argument elf is ignored, and the previous contents of file referenced by argument fd are overwritten.

Processing ar(1) archives

Random access within an opened archive is possible using the elf_next3 and elf_rand3 functions.

The symbol table of the archive may be retrieved using elf_getarsym3.  

RETURN VALUES

EXAMPLES

Elf_Cmd c;
Elf *ar_e, *elf_e;
...
c = ELF_C_READ;
if ((ar_e = elf_begin(fd, c, (Elf *) 0)) == 0) {
        ... handle error in opening the archive ...
}
while ((elf_e = elf_begin(fd, c, ar_e)) != 0) {
        ... process member referenced by elf_e here ...
        c = elf_next(elf_e);
        elf_end(elf_e);
}

To create a new ELF file, use:

int fd;
Elf *e;
...
if ((fd = open("filename", O_RDWR|O_TRUNC|O_CREAT, 0666)) < 0) {
        ... handle the error from open(2) ...
}
if ((e = elf_begin(fd, ELF_C_WRITE, (Elf *) 0)) == 0) {
        ... handle the error from elf_begin() ...
}
... create the ELF image using other elf(3) APIs ...
elf_update(e, ELF_C_WRITE);
elf_end(e);

ERRORS

Bq Er ELF_E_ARGUMENT

An unrecognized value was specified in argument cmd

Bq Er ELF_E_ARGUMENT

A non-null value for argument elf was specified when cmd was set to ELF_C_RDWR

Bq Er ELF_E_ARGUMENT

The value of argument fd differs from the one the ELF descriptor elf was created with.

Bq Er ELF_E_ARGUMENT

Argument cmd differs from the value specified when ELF descriptor elf was created.

Bq Er ELF_E_ARGUMENT

Argument elf was not a descriptor for an ar(1) archive.

Bq Er ELF_E_ARGUMENT

An ar(1) archive was opened with with cmd set to ELF_C_RDWR

Bq Er ELF_E_IO

Function elf_begin ();
was unable to truncate a file opened for writing using ELF_C_WRITE

Bq Er ELF_E_RESOURCE

An out of memory condition was encountered.

Bq Er ELF_E_SEQUENCE

Function elf_begin ();
was called before a working version was established with elf_version3.

SEE ALSO

Index

NAME

LIBRARY

SYNOPSIS

DESCRIPTION

Processing ar(1) archives

RETURN VALUES

EXAMPLES

ERRORS

SEE ALSO

Партнёры:

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