execv()

[lukego]

Seems that ljsyscall provides execve() but not execv(). Is there a simple way to emulate the latter? (I want the new process image to inherit the environment.)

My first attempt did not work:

S.execve("/bin/ls", "", S.environ())
Error in syscall/syscalls.lua:568: cannot convert 'string' to 'const char *[?]'

[justincormack]

Yes, we should provide a conversion function here for this use case, makes sense.

On 11 Nov 2016 1:07 p.m., "Luke Gorrie" notifications@github.com wrote:

Seems that ljsyscall provides execve() but not execv(). Is there a simple way to emulate the latter? (I want the new process image to inherit the environment.)

My first attempt did not work:

S.execve("/bin/ls", "", S.environ()) Error in syscall/syscalls.lua:568: cannot convert 'string' to 'const char *[?]'

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[lukego]

Could also be that I misdiagnosed my problem here. The error seems to be because I am passing a bad argv ("" instead of {}). Maybe S.environ() actually does work for passing the existing environment?

[lukego]

@justincormack JFYI it took me a while to understand why I could not pass my current environment to a new process like this:

S.execve(cmd, argv, S.environ())

and eventually realized while looking at strace that no environment is passed in this case. I suppose that S.environ() is returning a table with string keys while S.execve() is expecting an array of key=value strings. I suppose this is a Lua-ism where ljsyscall will iterate through the array part of the table with pairs() and think it is empty i.e. silently ignore the hash part.

This is what I am doing instead right now:

local env = {}
for key, value in pairs(S.environ()) do
   table.insert(env, key.."="..value)
end
S.execve(cmd, argv, env)

[lukego]

(Closing since this seems to be working fine and I just needed to work out the API.)