在python中使用命令行参数将变量设置为c程序的输出

Question

I am trying to use a python script in which a variable is set to the output of ac program test.c which requires command line arguments. Below is my c program:

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>

int main(int argc, char *argv[])
{
       int lat;
       lat=atoi(argv[1]);
       printf("-->%d\n",lat);
}

The python program is:

  import subprocess

  for lat in range(80,-79,-1):
           cmd = '"./a.out" {}'.format(lat)
           print "cmd is ",cmd
           parm31=subprocess.call(cmd,shell=True)
           print "parm is ",parm31

I have compiled test.c to get a.out. My goal is to have an output when running the python program with the c program (test.c or a.out) embedded in it is to have an output of:

 parm is -->80
 parm is -->79
 parm is -->78
 ...
 parm is -->-77
 parm is -->-78

I am unfortunately not getting to output but other values for the number component of the variable and some other undesired output. How do I tweak this program in order to get the correct output?

Answer 1

According to [Python 2.Docs]: subprocess. call ( args, *, stdin=None, stdout=None, stderr=None, shell=False ) ( emphasis is mine):

Run the command described by args . Wait for command to complete, then return the returncode attribute .

To make things work:

• Use check_output instead
• Make the command to be carried a list (not string)
• Don't pass shell=True

import subprocess

for lat in range(80, -79, -1):
    cmd = ["\"./a.out\"", "{}".format(lat)]
    print "Command is ", " ".join(cmd)
    out = subprocess.check_output(cmd)
    print "Command output is ", out.strip()