I'm doing os.system to tail for a live file and grep for a string
How can I execute something when the grep succeeds?
For example
cmd= os.system(tail -f file.log | grep -i abc)
if (cmd):
#Do something and continue tail
Is there any way I can do this? It will only come to the if block when the os.system statement is completed.
You can use subprocess.Popen and read lines from stdout:
import subprocess
def tail(filename):
process = subprocess.Popen(['tail', '-F', filename], stdout=subprocess.PIPE)
while True:
line = process.stdout.readline()
if not line:
process.terminate()
return
yield line
For example:
for line in tail('test.log'):
if line.startswith('error'):
print('Error:', line)
I am not sure that you really need to do this in python - perhaps it would e easier to pipe the tail-f output into awk: https://superuser.com/questions/742238/piping-tail-f-into-awk
If you want to work in python (because you need to do some processing afterwards) then check this link on how to use tail -f: How can I tail a log file in Python?
