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POTcl/Expect regular expression - want to make lazy (as opposed to greedy)
 

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  1. POTcl/Expect regular expression - want to make lazy (as opposed to greedy)
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    <p>New to the site, so bear with me. I'm working on a Tcl/Expect script and trying to match part of the 4th line in the following router output (two possible outputs shown). It will usually have an IP address, but may have a string like in the second sample:</p> <pre><code>Routing entry for 10.1.1.0/30 Known via "static", distance 1, metric 0 Routing Descriptor Blocks: * 10.3.3.1 Route metric is 0, traffic share count is 1 </code></pre> <p>Another possible output:</p> <pre><code>Routing entry for 10.1.2.0/24 Known via "static", distance 220, metric 0 (connected) Advertised by bgp 1234 Routing Descriptor Blocks: * directly connected, via Null0 Route metric is 0, traffic share count is 1 </code></pre> <p>My expect statement, using regexp, is the following:</p> <pre><code>expect -re "Routing Descriptor Blocks:\r\n \\\* (.*)\r\n" { set next_hop $expect_out(1,string) puts "\n\n*Next-hop address is: $next_hop*\n" } </code></pre> <p>(The 3 backslashes are so that they get through Tcl parsing, and a * is handed to the regexp interpreter, to match a literal asterisk.)</p> <p>My problem is that - not surprisingly - this is doing a "greedy" match, and I need it NOT to be greedy. See debug output, where this is made clear:</p> <pre><code>expect: does "show ip route 10.1.1.0\r\nRouting entry for 10.1.1.0/30\r\n Known via "static", distance 1, metric 0\r\n Routing Descriptor Blocks:\r\n * 10.3.3.1\r\n Route metric is 0, traffic share count is 1\r\n\r\nRouter&gt;" (spawn_id 4) match regular expression "Routing Descriptor Blocks:\r\n \* (.*)\r\n"? yes expect: set expect_out(0,string) "Routing Descriptor Blocks:\r\n * 10.3.3.1\r\n Route metric is 0, traffic share count is 1\r\n\r\n" expect: set expect_out(1,string) "10.3.3.1\r\n Route metric is 0, traffic share count is 1\r\n" </code></pre> <p>I would like the match to stop at the FIRST \r\n.</p> <p>So, for non-greedy match, I would have thought I needed to add an "?" as follows:</p> <pre><code>expect -re "Routing Descriptor Blocks:\r\n \\\* (.*?)\r\n" { set next_hop $expect_out(1,string) puts "\n\n*Next-hop address is: $next_hop*\n" } </code></pre> <p>Problem is, this does not seem to work. I get the following from the debug output:</p> <pre><code>bad regular expression: nested *?+ while executing "expect -re "Routing Descriptor Blocks:\r\n \\\* (.*?)\r\n" { set next_hop $expect_out(1,string) puts "\n\n*Next-hop address is: $next_hop*\n" }" (file "./test_telnet_to_router.exp" line 23) </code></pre> <p>I've been staring at this for too long now, so thought I would request some help. Any ideas on what I need to do to get the lazy match I need? Pls note that I'm stuck with using just Basic Regular Expressions on this HP-UX server... Extended Regular Expressions are not available.</p> <p>Thanks, James</p>
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    1. USJames
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    1. COWhat Tcl version is this? (in an interactive expect or tclsh session, `info patchlevel`)
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      1. POTcl/Expect regular expression - want to make lazy (as opposed to greedy)
      1. USglenn jackman
    2. COexpect1.1> info patchlevel 7.4 Thanks for taking the time of looking at this!
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      1. POTcl/Expect regular expression - want to make lazy (as opposed to greedy)
      1. USJames
 

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