Regular expressions in expect

问题

I just started learning expect scripting.I have been trying to extract the following from my output:

core.4046140998.01.10.133211

with an expect script using the following command.can somebody please tell me where I am going wrong?I want to get to store this entire string i.e.( core.4046140998.01.10.133211*) in a variable and perform some action with it.

expect -re {^(core)\.*} {puts $expect_out(0,string)}

Do i have to import any packages in expect to make this work?

回答1:

Since this is expect, "core" may appear at the beginning of a line, but not at the beginning of the input string. To demonstrate:

$ expect
expect1.1> spawn sh
spawn sh
8043
expect1.2> send "echo core.1234\r"
expect1.3> exp_internal 1
expect1.4> expect -re {^core.*}
Gate keeper glob pattern for '^core.*' is 'core*'. Activating booster.

expect: does "" (spawn_id exp6) match regular expression "^core.*"? Gate "core*"? gate=no
sh-4.3$ echo core.1234
core.1234
sh-4.3$ 
expect: does "sh-4.3$ echo core.1234\r\ncore.1234\r\nsh-4.3$ " (spawn_id exp6) match regular expression "^core.*"? Gate "core*"? gate=yes re=no
expect: timed out
expect1.5> expect -re {(?n)^core.*}
Gate keeper glob pattern for '(?n)^core.*' is 'core*'. Activating booster.

expect: does "sh-4.3$ echo core.1234\r\ncore.1234\r\nsh-4.3$ " (spawn_id exp6) match regular expression "(?n)^core.*"? Gate "core*"? gate=yes re=yes
expect: set expect_out(0,string) "core.1234\r"
expect: set expect_out(spawn_id) "exp6"
expect: set expect_out(buffer) "sh-4.3$ echo core.1234\r\ncore.1234\r"
expect1.6> puts ">>>$expect_out(0,string)<<<"
<<<core.1234

Things to note:

expecting -re {^core.*} did not match. We see the "timed out" message

note what we're attempting to match:

expect: does "sh-4.3$ echo core.1234\r\ncore.1234\r\nsh-4.3$ " (spawn_id exp6) match regular expression "^core.*"? Gate "core*"? gate=yes re=no
# ............^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

It starts with the command I sent, so using a "normal" anchor won't work

the next thing I expect is -re {(?n)^core.*}. This does match.
- the (?n) is a little-used Tcl regex instruction that tells the regex engine we want "newline-sensitive" matching.
- newline-sensitive matching means that . will not match a newline and (more relevant here) that ^ can match immediately after a newline within a multi-line string (similarly for $)
note that the output of my puts command looks odd. That's due to the carriage return at the end of $expect_out(0,string). Be aware of that, and use string trim as required

The take-away lessons here are:

extracting the output of commands can be hard in expect because the prompt and the sent command can get in the way.
use expect debugging to see why your patterns aren't matching.

回答2:

You have missed a . after \.:

^(core)\..*(\*)$

\. matches a literal . and . matches any single character.

Or you can use the non-greedy version:

^(core)\.[^*]*(\*)$

来源：https://stackoverflow.com/questions/37252842/regular-expressions-in-expect

标签

regex

expect