Linux System Administration

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Chapter 10: Scripting

Python has an equivalent to Perl’s getpwent function that enables us to restrict the

search to the field that contains names. Save the following script as finduser.py:

#!/usr/bin/python

import re, sys, pwd

pattern = "(?i)" + sys.argv[1]

for line in pwd.getpwall( ):

if re.search(pattern, line.pw_gecos):

print line

Now let’s see how it works:

admin@server1:~$ ./finduser.py alf

('adedarc', 'x', 501, 501, 'Alfredo de Darc', '/home/adedarc', '/bin/bash')

In this script, the line we printed was a Python list rather than a string, and it was

pretty-printed. To print the line in its original format, use this:

#!/usr/bin/python

import re, sys, pwd

pattern = "(?i)" + sys.argv[1]

for line in pwd.getpwall( ):

if re.search(pattern line.pw_gecos):

print ":".join(["%s" % v for v in line])

The last line is needed to turn each field into a string (pw_uid and pw_gid are inte-

gers) before joining them into one long, colon-separated string. Although Perl and

PHP let you treat a variable as a string or a number, Python is stricter.

The final step is to restrict the searches to accounts with uid > 500:

#!/usr/bin/python

import re, sys, pwd

pattern = "(?i)" + sys.argv[1]

for line in pwd.getpwall( ):

if line.pw_uid > 500 and re.search(pattern line.pw_gecos):

print ":".join(["%s" % v for v in line])

Choosing a Scripting Language

The choice of a programming language, like the choice of a text editor ...