python3 sys.exit vs SystemExit

Question

New to Python 3, and running into an issue I'm having trouble debugging. When the status prints using sys.exit, the output from my print statement gets cut off to one line, but when I use SystemExit it prints all of the output. Can anyone explain this to me please?

import psutil
import sys

def mountpoint():
    output = psutil.disk_partitions(all=False)
    marray = []
    #create a list from the disk partitions function
    for fs in output:
        marray.append(fs.mountpoint)
    return marray

def usage():
    uarray = {}
    for i in mountpoint():
        #create a dictionary with mountpoint as the key and the usage percentage as the value
        uarray[i] = psutil.disk_usage(i).percent
    return uarray

diskUsage = usage()

#Icinga errors
s = "SEVERE -"
c = "CRITICAL -"
w = "WARNING -"
o = "OK -"
u = "UNKNOWN -"

for key, value in diskUsage.items():
    if value == 100:
        print("{0} {1}% used on {2}".format(s,value,key))
        sys.exit(2)
    elif value >= 95 and value < 100:
        print("{0} {1}% used on {2}".format(c,value,key))
        sys.exit(2)
    elif value >= 92 and value < 95:
        print("{0} {1}% used on {2}".format(w,value,key))
        sys.exit(1)
    elif value < 92 and value > 0:
        print("{0} {1}% used on {2}".format(o,value,key))
        sys.exit(0)
    else:
        print("UNKNOWN - Unable to pull file-system usage or a non int value was stored")
        sys.exit(3)

EDIT

The following did not work:

elif value < 92 and value > 0:
        print("{0} {1}% used on {2}".format(o,value,key))
        sys.stdout.flush()
        sys.exit(0)

elif value < 92 and value > 0:
        print("{0} {1}% used on {2}".format(o,value,key), file=sys.stderr)
        sys.exit(0)

elif value < 92 and value > 0:
            print("{0} {1}% used on {2}".format(o,value,key), flush=True)
            sys.exit(0)

This prints the full output:

elif value < 92 and value > 0:
            print("{0} {1}% used on {2}".format(o,value,key))
            SystemExit(0)

The desired output is with SystemExit(0):

OK - 1.8% used on /
OK - 35.7% used on /boot

The output i'm getting with sys.exit(0):

OK - 1.8% used on /

Try using print('message', file=sys.stderr). Does that change anything? It may be related to fact that stdout would be buffered and not necessarily written straight away. Alternatively add before the exit sys.stdout.flush(). But why are you using sys.exit(0) in the first place, rather than using break and letting it drop out of the loop and then exit the script normally. — Graham Dumpleton
– Graham Dumpleton, Commented Dec 15, 2016 at 3:11
Thanks for the answers, i'm using the sys.exit(0) to capture the specific exit code for nagios to pick it up. I'm going to try the suggestions now and report back. EDIT This did not work: elif value < 92 and value > 0: print("{0} {1}% used on {2}".format(o,value,key)) sys.stdout.flush() sys.exit(0) — james.sadler519
– james.sadler519, Commented Dec 15, 2016 at 3:21
I've added: print("{0} {1}% used on {2}".format(o,value,key), file=sys.stderr) print("{0} {1}% used on {2}".format(o,value,key), flush=True) and sys.stdout.flush() between the print and sys.exit(0) none of these worked — james.sadler519
– james.sadler519, Commented Dec 15, 2016 at 3:26
Add these to your question so the question and the things you've tried are clearer. — pvg
– pvg, Commented Dec 15, 2016 at 3:33

user2357112 · Accepted Answer · 2016-12-15 03:56:34Z

5

SystemExit(0)

That doesn't actually exit. It just builds an exception object and throws it away. You would need to raise SystemExit(0) to actually exit.

When the status prints using sys.exit, the output from my print statement gets cut off to one line

Well, yeah. That's because you printed one line and then exited. Why are you calling sys.exit at all? If you want to set the process's exit code, call sys.exit once you're actually done.

answered Dec 15, 2016 at 3:56

user2357112

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