Linux System Administration

Scripting Language Shootout

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• Shell scripts run slower.

• Shell syntax is icky.

Perl initially filled the gap as administrators looked for more productive tools, but

now PHP has migrated out of its web niche, and Python has gained a reputation for

productivity. We’ll write one application in each of these languages; several others,

such as Ruby and Tcl, are also available on Linux.

Our application will search the /etc/passwd file for name, user ID, hat size, or what-

ever else we can find in there. You’ll see how to open a file, read records, parse for-

mats, search for patterns, and print results. Then we’ll look at ways to avoid some of

this work, because sweat

!= productivity. You’ll be able to apply these techniques to

other files, such as logs or web pages. This is an example of data munging, and you’re

probably doing a lot of it already.

Let’s invent some requirements for our application and express them with this

pseudocode:

read a search string from the user

open the places file

for each line:

parse the fields (columns)

search the name field for a match

if there's a match:

print the other fields in a readable format

By now, many programmers would have rushed in and started typing (some without

having read the data format or requirements). Readers of this book are more disci-

plined, though, as well as better looking. They’ve had to fix the messes that the other

programmers have made and ...