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Help about "file" cmd

 
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# 1  
Old 07-20-2012
Help about "file" cmd
Code:
 file /sbin/ifconfig.net-tools 
/sbin/ifconfig.net-tools: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.16, stripped

Does someone know what's the "x86-64" how it get this?
what's the 2.6.16, how it get this

and in some other linux os
Code:
/sbin/ifconfig: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.15, stripped

what is the Intel 80386, can some one explain, how it get this
# 2  
Old 07-20-2012
file command uses (/etc/magic or /usr/share/magic or /usr/share/file/magic) and reads the first few bytes of the file. It then tries to decode The first n bytes and then does a lookup on those bytes in the magic file. The text you see is in the magic file.

The size of n depends on the OS.
# 3  
Old 07-21-2012
Quote:
Originally Posted by jim mcnamara
file command uses (/etc/magic or /usr/share/magic or /usr/share/file/magic) and reads the first few bytes of the file. It then tries to decode The first n bytes and then does a lookup on those bytes in the magic file. The text you see is in the magic file.

The size of n depends on the OS.
But I can't find where tell "2.6.16"
# 4  
Old 07-21-2012
Quote:
Originally Posted by yanglei_fage
But I can't find where tell "2.6.16"
You won't find that in the magic file. Once file determines that it is dealing with an elf executable, it examines various sections of the elf binary for information left behind by the toolchain that built the binary.

For example, the vendor information is in a PT_NOTES section, PT_INTERP/PT_DYNAMIC can be used to determine if the binary is statically or dynamically linked, etc. You can't use grep on the binary because a lot of this information is in a binary format (for example, the vendor name and ABI version numbers).

What are you trying to accomplish?

Regards,
Alister
# 5  
Old 07-22-2012
Quote:
Originally Posted by alister
You won't find that in the magic file. Once file determines that it is dealing with an elf executable, it examines various sections of the elf binary for information left behind by the toolchain that built the binary.

For example, the vendor information is in a PT_NOTES section, PT_INTERP/PT_DYNAMIC can be used to determine if the binary is statically or dynamically linked, etc. You can't use grep on the binary because a lot of this information is in a binary format (for example, the vendor name and ABI version numbers).

What are you trying to accomplish?

Regards,
Alister

I want to know how "x86-64" is got and how is "GNU/Linux 2.6.16" got,
the info is determined by gcc or glibc, where can I find the source code to dertermine its"x86-84" but not i386, where can I find the source code it's "2.6.16" but not "2.6.36"

Thanks for the help

Lei
# 6  
Old 07-22-2012
Read up on the ELF specification. It's all in there.
 
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