Linux bin to header

How to view files in binary from bash?

I would like to view the contents of a file in the current directory, but in binary from the command line. How can I achieve this?

13 Answers 13

xxd does both binary and hexadecimal.

This has the advantage over «hexdump» that it also shows the ASCII form on the side, making it easier to identify the location I want to look at.

And to dump the output to an ASCII text file for perusing & searching: xxd file > hex_dump_of_file.txt

a supplment: xxd is not only for linux shell. I think it comes with vim. I had vim installed on windows, and I just found I can use xxd in windows too.

unless you want to edit it of course. Most linux distros have hexdump by default (but obviously not all).

I like this idea, but like the other suggestions it only outputs hex. Obviously this is much more compact than binary, but I am dealing with very small files so binary is preferred. Is hex the only way I will be able to view the file?

Well how small is the file? Anything over a couple of bytes and you will start to lose your mind using binary anyway. Hex makes much more sense for most things. If you are uncomfortable with hex just locate the bytes in which you are interested and convert them using a hex calculator.

I need to make sure that my file is compressing correctly and I don’t know what it should look like in hex (the size of each unit is 7 bits), so I would have to crunch the numbers by hand.

do you have any methods to see text from binary file? I can get HEX code, but how should i decode it to normal human text?

Type :%!xxd to view the hex strings, the n :%!xxd -r to return to normal editing.

As a fallback there’s always od -xc filename

sudo apt-get install bless

Bless is GUI tool which can view, edit, seach and a lot more. Its very light weight.

If you want to open binary files (in CentOS 7):

The best answer hands down. This converts the Binary file into a JSON file. Not all heros wear capes,that is true

It doesn’t convert it into JSON file. It only finds the printable strings in an object and show you. It doesn’t convert the binary file into text or any format at all.

$ echo -n 'Hello world!' | hd 00000000 48 65 6c 6c 6f 20 77 6f 72 6c 64 21 |Hello world!| 0000000c 

Hexyl formats nicely: sudo apt install hexyl

You can open emacs (in terminal mode, using emacs -nw for instance), and then use Hexl mode: M-x hexl-mode .

To get the output all in a single line in Hexadecimal:

xxd -p yourfile.bin | tr -d '\n' 

to convert a file to its binary codes(hexadecimal representation) we say:

to see all the contents and codes in a binary file , we could use commands like readelf and objdump , hexdump . .

for example if we want to see all the convert all the contents of a binary file(executable, shared libraries, object files) we say:

but readelf is the best utility for analyzing elf(executable and linking format) files. so if we say:

all the contents in the binary file bash would be shown to us, also we could provide different flags for readelf to see all the sections and headers of an elf file separately, for example if we want to see only the elf header we say:

for reading all the segments of the file:

for reading all the sections of the file:

but again as summary , for reading a normal file like «hello.c» and a binary file like bash in path /bin/bash in linux we say:

xxd hello.c readelf -a /bin/bash 

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Binary to Header

bin2header takes any file as an argument and converts its binary data into a source header file for use in C/C++ applications. The data is stored as a character array.

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shell-script headers (#!/bin/sh vs #!/bin/csh)

For a csh script, you should use #!/bin/csh -f ; the -f tells the shell not to source the user’s .login and .cshrc , which makes the script run faster and avoids dependencies on the user’s setup. (Or better yet, don’t write csh scripts.) Don’t use -f for sh or bash scripts; it doesn’t have the same meaning.

it’s a fair question and a classic but «is it required» can also be answered empirically. Mostly. no, not at all.

3 Answers 3

This is known as a Shebang :

A shebang is only relevant when a script has the execute permission (e.g. chmod u+x script.sh).

When a shell executes the script it will use the specified interpreter.

#!/bin/bash # file: foo.sh echo 1 $ chmod u+x foo.sh $ ./foo.sh 1 

@Kolob Canyon you do not need to, but it can help some editors with syntax highlighting (although there are usually other ways to achieve the same thing): unix.stackexchange.com/a/88730/193985

The #! line tells the kernel (specifically, the implementation of the execve system call) that this program is written in an interpreted language; the absolute pathname that follows identifies the interpreter. Programs compiled to machine code begin with a different byte sequence — on most modern Unixes, 7f 45 4c 46 ( ^?ELF ) that identifies them as such.

You can put an absolute path to any program you want after the #! , as long as that program is not itself a #! script. The kernel rewrites an invocation of

where ./script starts with, say, #! /usr/bin/perl , as if the command line had actually been

/usr/bin/perl ./script arg1 arg2 arg3 

Or, as you have seen, you can use #! /bin/sh to write a script intended to be interpreted by sh .

The #! line is only processed if you directly invoke the script ( ./script on the command line); the file must also be executable ( chmod +x script ). If you do sh ./script the #! line is not necessary (and will be ignored if present), and the file does not have to be executable. The point of the feature is to allow you to directly invoke interpreted-language programs without having to know what language they are written in. (Do grep ‘^#!’ /usr/bin/* — you will discover that a great many stock programs are in fact using this feature.)

Here are some rules for using this feature:

• The #! must be the very first two bytes in the file. In particular, the file must be in an ASCII-compatible encoding (e.g. UTF-8 will work, but UTF-16 won’t) and must not start with a «byte order mark», or the kernel will not recognize it as a #! script.
• The path after #! must be an absolute path (starts with / ). It cannot contain space, tab, or newline characters.
• It is good style, but not required, to put a space between the #! and the / . Do not put more than one space there.
• You cannot put shell variables on the #! line, they will not be expanded.
• You can put one command-line argument after the absolute path, separated from it by a single space. Like the absolute path, this argument cannot contain space, tab, or newline characters. Sometimes this is necessary to get things to work ( #! /usr/bin/awk -f ), sometimes it’s just useful ( #! /usr/bin/perl -Tw ). Unfortunately, you cannot put two or more arguments after the absolute path.
• Some people will tell you to use #! /usr/bin/env interpreter instead of #! /absolute/path/to/interpreter . This is almost always a mistake. It makes your program’s behavior depend on the $PATH variable of the user who invokes the script. And not all systems have env in the first place.
• Programs that need setuid or setgid privileges can’t use #! ; they have to be compiled to machine code. (If you don’t know what setuid is, don’t worry about this.)

Regarding csh , it relates to sh roughly as Nutrimat Advanced Tea Substitute does to tea. It has (or rather had; modern implementations of sh have caught up) a number of advantages over sh for interactive usage, but using it (or its descendant tcsh ) for scripting is almost always a mistake. If you’re new to shell scripting in general, I strongly recommend you ignore it and focus on sh . If you are using a csh relative as your login shell, switch to bash or zsh , so that the interactive command language will be the same as the scripting language you’re learning.

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How to convert Linux kernel Bin into ELF format

We have a Linux kernel binary which is without an ELF header, and our bootloader will be loading the kernel image (earlier QNX kernel image has the ELF header) based on a calculation coming from the ELF header, but since our Linux kernel image is without an ELF header, our bootloader is denying loading of this kernel image to memory. For some reasons we don’t have an option to alter our bootloader code, so the only option we have is to insert an ELF header into the Linux BIN file with a particular entry point. What is the way to achieve it?

1 Answer 1

The objcopy command is able to wrap a binary file with an appropriate ELF header. For example, the following command will convert the binary file input.in into an i386 object file output.o :

objcopy -I binary -O elf32-i386 --binary-architecture i386 input.bin output.o 

Three symbols will be defined in output.o : _binary_input_bin_start , _binary_input_bin_end and _binary_input_bin_size . Additionally, that data of your input file will be in a .data section.

You will then need to use ld with a linker script to set the appropriate load/virtual/physical addresses and entry points. The following is a minimal script:

but will likely need to be heavily modified depending on precisely how your bootloader works, your physical memory layout, where you want to kernel located, your architecture, etc. Once tweaked, it can then be used to generate your final ELF file as follows:

ld -m elf_i386 output.o -T binary.ld -o output.elf 

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