os.system() 和 os.popen()
1. os.system()
os.system 直接执行命令，执行成功返回0.
>>> a = os.system('ls')
bin dev initrd.img lib32 media proc scratch sys var
boot etc initrd.img.old lib64 mnt root selinux tmp vmlinuz
cdrom home lib lost+found opt sbin srv usr vmlinuz.old
>>> a
0
2. os.popen()
os.popen() 将运行结果作为一个 file object 返回。
>>> a = os.popen('ls')
>>> a
<open file 'ls', mode 'r' at 0x7f866451ddb0>
>>> a.readlines()
['bin\n', 'boot\n', 'cdrom\n', 'dev\n', 'etc\n', 'home\n', 'initrd.img\n', 'initrd.img.old\n', 'lib\n', 'lib32\n', 'lib64\n', 'lost+found\n', 'media\n', 'mnt\n', 'opt\n', 'proc\n', 'root\n', 'sbin\n', 'scratch\n', 'selinux\n', 'srv\n', 'sys\n', 'tmp\n', 'usr\n', 'var\n', 'vmlinuz\n', 'vmlinuz.old\n']
