Example of evaluating c structs from c function calls from Julia. N.B. C struct types are of the OSX variant

c-struct-to-julia.jl

type c_passwd
    pw_name::Ptr{Uint8}
    pw_passwd::Ptr{Uint8}
    pw_uid::Int32
    pw_gid::Int32
    pw_change::Int32
    pw_class::Ptr{Uint8}
    pw_gecos::Ptr{Uint8}
    pw_dir::Ptr{Uint8}
    pw_shell::Ptr{Uint8}
    pw_expire::Int32
    pw_fields::Int32
end

type j_passwd
    cpwd::c_passwd
    name::ASCIIString
    passwd::ASCIIString
    uid::Int32
    gid::Int32
    change::Int32
    pw_class::ASCIIString
    gecos::ASCIIString
    dir::ASCIIString
    shell::ASCIIString
    expire::Int32
    fields::Int32
end

function j_passwd(pt::Ptr{c_passwd})
    cpwd = unsafe_ref(pt)
    j_passwd(cpwd, bytestring(cpwd.pw_name), 
                   bytestring(cpwd.pw_passwd), 
                   cpwd.pw_uid, 
                   cpwd.pw_gid, 
                   cpwd.pw_change, 
                   bytestring(cpwd.pw_class), 
                   bytestring(cpwd.pw_gecos), 
                   bytestring(cpwd.pw_dir), 
                   bytestring(cpwd.pw_shell), 
                   cpwd.pw_expire, 
                   cpwd.pw_fields)
end

for i=1:300
  getpwuid_ret = ccall((:getpwuid,:libc), Ptr{c_passwd}, (Int32,), i)
  if getpwuid_ret != C_NULL
    pw_entry = j_passwd(getpwuid_ret)
    println("$(pw_entry.uid): $(pw_entry.name), $(pw_entry.shell), $(pw_entry.dir)")
  end
end