61 byte shellcode

[bits 32]
; the following is 61 bytes when assembled
    push byte 0x4   ; 0x4 == sys_write
    pop eax         ;
    lea edx, [eax + eax*2] ; string length to print == 12

    push byte 0x1   ; where to write, 0x1 == stdout
    jmp SHORT data_segment
_databack:
    ; first time here pops pointer to mystr
    ; 2nd time pops pointer pointer argv
    pop ecx

    ; first time here pops 0x1
    ; 2nd time pops pointer argv[0]
    pop ebx;
    int 0x80    ; execute syscall

    cdq             ; zero edx
    push edx        ; zero terminate argv
    lea ecx, [ecx+2*eax]; point to arg1 str
    push ecx        ; arg1
    dec ecx     ; point to end of previous string
    mov [ecx],dl    ; zero terminate arg0
    dec eax     ; eax holds returnvalue of 12 (length of str printet)
    sub ecx, eax    ; point to beginning of arg0
    push ecx        ; arg0
    push esp    ; esp is a pointer pointer to argv
    jmp SHORT _databack
data_segment:
    call _databack ; trampoline
    mystr db "hello world",0xa,"/usr/bin/id -u"