[Answer]-Django web application race-condition on file

it seems like you use a single file /home/user/file.c for every request. so, race condition is imminent.

there are two solutions :

1) write to a temporary file. temporary file can be generated from tempfile module, or you can just create random filename.

2) write to a memory file. you can use StringIO (or faster cStringIO) module to create such file, and then you can pipe it to gcc.

for solution 1), there are many ways to do this but here’s my solution:

change this part

data=request.GET.get('content','')
handle=open('/home/user/file.c','r+')
handle.write(request.GET['content'])
handle.close()

to

# you need 'random', 'string', 'os' modules imported
data=request.GET.get('content','')
filename = "".join(random.sample(string.letters, 10)) + ".c" #sample 10 letters from A-z
filepath = os.path.join('home','user','filename')
handle=open(filepath,'r+')
handle.write(request.GET['content'])
handle.close()
res = commands.getstatusoutput('gcc -Wall %s -o /home/user/file;home/user/file' %filepath)
os.remove(filepath) #remove temporary file after compiling

also, the commands module is deprecated. you should use subprocess.call.

You should generate random file with each request and use that. The tempfile module can help you with that.

Also if you don’t care about produced binary, using -o /dev/null is good idea.