How can I get the architecture of a '.a' file?

Question

I have a .a file from which I want to get architecture information. Running file myFile.a results in file.a: current ar archive. How can I get more information on what architecture the file contains?

Answer 1

http://linux.die.net/man/1/ar

extract the object files from the archive and inspect them with file(1), nm(1), etc.

Answer 2

You can also skip the ar command and use readelf, via something like:

readelf -h <archive>.a | grep 'Class\|File\|Machine'

[00:32:15] /usr/lib $ readelf -h libxslt.a | grep 'Class\|File\|Machine'
File: libxslt.a(attrvt.o)
  Class:                             ELF32
  Machine:                           Intel 80386
File: libxslt.a(xslt.o)
  Class:                             ELF32
  Machine:                           Intel 80386
... #Trimmed this, it goes on a bit
File: libxslt.a(transform.o)
  Class:                             ELF32
  Machine:                           Intel 80386
File: libxslt.a(security.o)
  Class:                             ELF32
  Machine:                           Intel 80386
[00:32:24] /usr/lib $

---

In case it's relevant, here's the other information that you can get from readelf -h. I just trimmed the above with grep, obviously:

File: libxslt.a(security.o)
ELF Header:
  Magic:   7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00 
  Class:                             ELF32
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              REL (Relocatable file)
  Machine:                           Intel 80386
  Version:                           0x1
  Entry point address:               0x0
  Start of program headers:          0 (bytes into file)
  Start of section headers:          2548 (bytes into file)
  Flags:                             0x0
  Size of this header:               52 (bytes)
  Size of program headers:           0 (bytes)
  Number of program headers:         0
  Size of section headers:           40 (bytes)
  Number of section headers:         16
  Section header string table index: 13

That output is for one of the object files in libxslt.a, but it gives the same information for each file.

Answer 3

objdump is another option:

objdump -a file.a|grep 'file format'