There are 9 program headers, starting at offset 64 The switch -l (short for –program-headers or –segments) reveals more details as shown in Listing 4.Listing 4: Display information about the program headers The header from Listing 2 shows that the ELF file consists of 9 program headers that have a size of 56 bytes each, and the first header starts at byte 64.Īgain, the readelf command helps to extract the information from the ELF file.
#Unix executable file converter online how to#
The program header shows the segments used at run-time, and tells the system how to create a process image. Section header string table index: 26 The Program Header Start of section headers: 58408 (bytes into file) Start of program headers: 64 (bytes into file) Listing 2: The hexdump of the binary file The hexdump of the binary file touch looks as follows. Among other values, the header also indicates whether it is an ELF file for 32 or 64-bit format, uses little or big endianness, shows the ELF version as well as for which operating system the file was compiled for in order to interoperate with the right application binary interface (ABI) and cpu instruction set. It starts with a sequence of four unique bytes that are 0x7F followed by 0x45, 0x4c, and 0x46 which translates into the three letters E, L, and F. The ELF header is 32 bytes long, and identifies the format of the file. Each segment contains information that is necessary for run-time execution of the file, while sections contain important data for linking and relocation. The file data section can consist of a program header table describing zero or more segments, a section header table describing zero or more sections, that is followed by data referred to by entries from the program header table, and the section header table. The two tables describe the rest of theĪs you can see from the description above, an ELF file consists of two sections – an ELF header, and file data. Header table and the section header table's offset in the file areĭefined in the ELF header. The ELF header is always at offset zero of the file. Object files, core files and shared libraries.Īn executable file using the ELF file format consists of an ELF header,įollowed by a program header table or a section header table, or both. Amongst these files are normal executable files, relocatable The header file defines the format of ELF executable binaryįiles. On a Linux terminal, the command man elf gives you a handy summary about the structure of an ELF file: Listing 1: The manpage of the ELF structureĮlf - format of Executable and Linking Format (ELF) files In use is a variety of letter combinations, such as. The specification does not clarify the filename extension for ELF files. Furthermore, you will find it on mobile devices running Android, Maemo or Meego OS/Sailfish OS as well as on game consoles like the PlayStation Portable, Dreamcast, and Wii. Among others, this includes Linux, Solaris/Illumos, Free-, Net- and OpenBSD, QNX, BeOS/Haiku, and Fuchsia OS. Since then, the ELF format is in use by several different operating systems. For a detailed comparison of executable file formats, have a look here. ELF’s design is not limited to a specific processor, instruction set, or hardware architecture. The reason behind that decision was the design of ELF – flexibility, extensibility, and cross-platform support for different endian formats and address sizes. This fact enormously simplified the agreement on standardization between the different vendors and developers of Unix-based operating systems. Luckily, the ELF format had been previously documented in both the System V Application Binary Interface, and the Tool Interface Standard. Twenty years ago – in 1999 – the 86open project has chosen ELF as the standard binary file format for Unix and Unix-like systems on x86 processors. It is widely used for executable files, relocatable object files, shared libraries, and core dumps. The binary file mentioned above follows a specific structure, and one of the most common ones is named ELF that abbreviates Executable and Linkable Format.
#Unix executable file converter online code#
This file contains the single instructions as machine code that are understood by the CPU, and are executed as soon the compiled program is run. Eventually, the linker translates the object code into a binary file that links the object code with the referenced libraries. With the help of an adequate compiler, for example GCC, your source code is translated into object code, first. Programming starts with having a clever idea, and writing source code in a programming language of your choice, for example C, and saving the source code in a file.
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