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5.7.3 Logging expect internal actions

With the ‘--debug’ option, you can request a log file showing the output from expect itself, running in debugging mode. This file (‘dbg.log’, in the directory where you start runtest) shows each pattern expect considers in analyzing test output.

This file reflects each send command, showing the string sent as input to the tool under test; and each expect command, showing each pattern it compares with the tool output.

The log messages for expect begin with a message of the form

 
expect: does {tool output} (spawn_id n) match pattern
{expected pattern}?

For every unsuccessful match, expect issues a ‘no’ after this message; if other patterns are specified for the same expect command, they are reflected also, but without the first part of the message (‘expect…match pattern’).

When expect finds a match, the log for the successful match ends with ‘yes’, followed by a record of the expect variables set to describe a successful match. Here is an excerpt from the debugging log for a GDB test:

 
send: sent {break gdbme.c:34\n} to spawn id 6
expect: does {} (spawn_id 6) match pattern {Breakpoint.*at.* file
 gdbme.c, line 34.*\(gdb\) $}? no
{.*\(gdb\) $}? no
expect: does {} (spawn_id 0) match pattern {<return>}? no
{\(y or n\) }? no
{buffer_full}? no
{virtual}? no
{memory}? no
{exhausted}? no
{Undefined}? no
{command}? no
break gdbme.c:34
Breakpoint 8 at 0x23d8: file gdbme.c, line 34.
(gdb) expect: does {break gdbme.c:34\r\nBreakpoint 8 at 0x23d8:
file gdbme.c, line 34.\r\n(gdb) } (spawn_id 6) match pattern
{Breakpoint.*at.* file gdbme.c, line 34.*\(gdb\) $}? yes
expect: set expect_out(0,start) {18}
expect: set expect_out(0,end) {71}
expect: set expect_out(0,string) {Breakpoint 8 at 0x23d8: file
gdbme.c, line 34.\r\n(gdb) }
expect: set expect_out(spawn_id) {6}
expect: set expect_out(buffer) {break gdbme.c:34\r\nBreakpoint 8
at 0x23d8: file gdbme.c, line 34.\r\n(gdb) }
        PASS:   70      0       breakpoint line number in file

This example exhibits three properties of expect and DejaGnu that might be surprising at first glance:


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