Shell Programming and Scripting

Hi FolksI want to write a nawk script that dynamically creates variable numbers of regular expressions on the fly rather than using constants. Is this possible?They would need to be used within an if statement within the nawk program: -

Code:

 if ( "my string of regex's" )

Thanks

Can you give more information what you are trying to achieve?

Hi Franklin

I can now, my computer at work can't seem to handle this site.

I have a very inefficient script that is looking at files full of ps output, 1 file for each server on the logical network. It is parsing a config file that contains entries pertaining to each process being monitored, between two and five lines of config per process.

I need to read in the entries from the config file containing patterns to match in the ps output, such as user, name of process, args etc.

So depending on how many args to match there are in the config file I need to create a regular expression to test or match or equal the patterns in the ps output.

So for one entry i may need to match two items and equal a string for example, the next I will need to build an expression that is different.

What would be most convenient would be to create the test in the if statement as a string and somehow eval it.

So if I could do something like: -

Code:

regex = "$0 ~ /name/"
if ( regex )
do something

So my question is "is that possible in awk"?

FWIK it isn't possible to load code dynamically with awk.

Regards

It is possible and common, but your code is incorrect. In your example, the if condition will evaluate to true if the value of regex is any non-null string. What you want is:

Code:

regex="name"
if ($0 ~ regex)
    do something

Thanks guys but I need to create multiple tests that are combinations of ~ and == tests

Guess I'll have to come up with a different approach

Thanks

An array of strings can represent the tests that need to succeed and a for loop can be used to iterate over that list. == can be simulated with ~ using an anchored expression without (or with escaped) metacharacters. Depending on whether the expressions themselves are dynamic or hardcoded, this may or may not be trivial.

As with all help requests, some actual examples or your current script would've been more informative than your textual descriptions.

Good luck,
Alister