Check string(line) in a file and send email

Question

I want to check some lines from a log file [check msyql replication slave status log] named "status.txt" (size is always about 3-4 KB):

Slave_IO_Running: Yes
Slave_SQL_Running: Yes

If any of these two line's value is 'No' then email is sent to [email protected]. These two lines are unique and both occur only once.

#!/usr/bin/python
import smtplib
import os
import email.Utils
from email.mime.text import MIMEText
import sys
i=0
for line in open("status.txt"):
 if "Slave_IO_Running: Yes" in line:
 print "match1",line
 i=i+1
 else:
 pass 
for line2 in open("status.txt"):
 if "Slave_SQL_Running: Yes" in line2:
 i=i+1
 else:
 pass
print i
if i<2:
 msg=MIMEText("Mysql not running")
 fromaddr="[email protected]"
 toaddr="[email protected]"
 server = smtplib.SMTP('localhost')
 server.set_debuglevel(1)
 server.sendmail(fromaddr, [toaddr], msg.as_string())
 server.quit()
else:
 print "mysql running OK" 

Please review my code.

Contents of "status.txt" file:

 Relay_Log_Pos: 195294327
 Relay_Master_Log_File: web01-bin.000001
 Slave_IO_Running: Yes
 Slave_SQL_Running: Yes
 Replicate_Do_DB: 
 Replicate_Ignore_DB:
mysql,information_schema,cphulkd,eximstats,horde,leechprotect,logaholicDB_web01,performance_schema,roundcube,whmxfer
 Replicate_Do_Table: 
 Replicate_Ignore_Table:

Answer 1

The else-pass construct is unnecessary. The else clause is not required. Leaving it of has the same result as what you have now.

---

You loop over the same file twice. Instead you can check the line for both messages in the same loop.

for line in open("status.txt"):
 if "Slave_IO_Running: Yes" in line or "Slave_SQL_Running: Yes" in line2:
 print "match",line
 i=i+1

---

However, the above change points out a potential bug. We don't have any information about what the contents of status.txt are. If it is possible for either of those strings to appear more than once, the code as posted (and my above update) could find two matches without finding a result for IO and SQL. ¹

sql_found = false
io_found = false
for line in open("status.txt"):
 if not io_found and "Slave_IO_Running: Yes" in line:
 print "match",line
 io_found = true
 if not sql_found and "Slave_SQL_Running: Yes" in line:
 print "match",line
 sql_found = true
if not sql_found or not io_found:
 # send email

---

If the status file is long, you can break out of the loop after both lines have been found. This would prevent unnecessary work when you already know the correct information.

---

i is not a good variable name. It does not convey any information about how it is being used. In addition, i is widely accepted as the variable name for indexing in a loop. In this code you are looping, but i is being used for something else. Changing the name will prevent any confusion.

---

You can use the with construct to ensure the file is closed when you are done with it.

with open(status) as f:
 for line in open("status.txt"):
 # operate on a line

This is a short running script, so it is not a huge deal, but it is a good practice to get into when you move to writing longer applications. While this is a short running

---

You never use sys, os or email.Utils. These imports can be removed.

---

¹: If we extrapolate on the idea that the line might show up more than once, that could also mean that the file could contain a Yes line followed by a No line. If this is the case, this simple loop logic would no longer be sufficient.