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Command Reference
Until a more detailed guide is written, we'll give an overview of trepan2 here. You can find where we're going by comparing with the manuals for pydb and ruby-debug.
Contents
The help system has been reworked from pydb and pdb and it is more extensive now. Play around with it. Starting with a plain help
(trepan2) helpClasses of commands:breakpoints -- Making the program stop at certain pointsdata -- Examining data...(trepan2) help breakpointsList of commands:break -- Set breakpoint at specified line or functioncondition -- Specify breakpoint number N ......(trepan2) help *List of all debugger commands: break enable ipython python source condition examine jump quit step ...You can set the line width to use in displaying the help output using
the command: set width. To see the current line width, initially
taken from the COLUMNS environment variable, type: show width.
The list command will show you your source code.
(trepan2) list21#!/usr/bin/python2"""Greatest Common Divisor 3 4 Some characterstics of this program used for testing check_args() does 5 not have a 'return' statement. 6 7 check_args() raises an uncaught exception when given the wrong number 8 of parameters. 9 10 -> """
(trepan2) list# keep going11importsys1213defcheck_args():
14iflen(sys.argv) !=3:
15# Rather than use sys.exit let's just raise an error16raiseException, "Need to give two numbers"17foriinrange(2):
18try:
19sys.argv[i+1] =int(sys.argv[i+1])
20exceptValueError:
(trepan2) importos.path# Assumes set autoeval on
(trepan2) listos.path1111"""Common operations on Posix pathnames. 2 3 Instead of importing this module directly, import os and refer to 4 this module as os.path. The "os.path" name is an alias for this 5 module on Posix systems; on other systems (e.g. Mac, Windows), 6 os.path provides the same operations in a manner specific to that 7 platform, and is an alias to another module (e.g. macpath, ntpath). 8 9 Some of this can actually be useful on non-Posix systems too, e.g. 10 for manipulation of the pathname component of URLs. 11 """
(trepan2) listos.path.join5152# Join pathnames.53# Ignore the previous parts if a part is absolute.54# Insert a '/' unless the first part is empty or already ends in '/'.5556defjoin(a, *p):
57"""Join two or more pathname components, inserting '/' as needed"""58path=a59forbinp:
60ifb.startswith('/'):
(trepan2) remember_this_line=17
(trepan2) listremember_this_line1213defcheck_args():
14iflen(sys.argv) !=3:
15# Rather than use sys.exit let's just raise an error16raiseException, "Need to give two numbers"17foriinrange(2):
18try:
19sys.argv[i+1] =int(sys.argv[i+1])
20exceptValueError:
21print"** Expecting an integer, got: %s"%repr(sys.argv[i])
(trepan2)There are many more options and possibilities so check out help list
for details. If you are not using trepan2 via some sort of front-end
program (e.g. I generally use my GNU Emacs
front-end. Also see
[#Set_Auto_List] below.
Here's a sample session using these commands:
(trepan2) setbasename# Short filenames in display
(trepan2) settrace# Show the events
(trepan2) step4line-gcd.py:13line-gcd.py:26line-gcd.py:40line-gcd.py:41
(gcd.py:41): <module>--41check_args()
(trepan2) s# 's' is an abbreviation for stepcall-gcd.py:13
(gcd.py:13): check_args->13defcheck_args():
(trepan2) step<# Step until the next returnline-gcd.py:14line-gcd.py:17line-gcd.py:18line-gcd.py:19line-gcd.py:17line-gcd.py:18line-gcd.py:19line-gcd.py:17return-gcd.py:17
(gcd.py:17): check_args<-17foriinrange(2):
(trepan2) settraceoff# That's enough tracing
(trepan2) next# like step but skips over function calls
(gcd.py:43): <module>--43 (a, b) =sys.argv[1:3]
(trepan2) # A carriage-return or empty command runs the last step/next
(gcd.py:44): <module>--44print"The GCD of %d and %d is %d"% (a, b, gcd(a, b))
(trepan2) s<# step until the next call
(gcd.py:26): gcd->26defgcd(a,b):
(trepan2) finish# run until return of *this* function; compare with s<
(gcd.py:38): gcd<-38returngcd(b-a, a)
(trepan2) retval# show the return value1
(trepan2)In this section we describe cool commands not generally found in other Python debuggers that you may want to experiment with.
In addition to the sub-commands that we describe in more detail, also look at:
- set autopython -- go into python automatically on every stop
- set trace -- turn on/off event tracing
- info threads -- show list of threads and where they are
Also check out the set, show, and info commands in general.
aliasalias-namedebugger-command
Add alias alias-name for a debugger command debugger-comand.
Add an alias when you want to use a command abbreviation for a command
that would otherwise be ambigous. For example, by default we make s
be an alias of step to force it to be used. Without the alias, s
might be step, show, or set among others
Example:
alias cat list # "cat myprog.py" is the same as "list myprog.py" alias s step # "s" is now an alias for "step". # The above example is done by default.
See also unalias and show alias.
unaliasalias-name
Remove alias alias-name.
See also alias.
macromacro-namelambda-object
Define macro-name as a debugger macro. Debugger macros get a list of arguments which you supply without parenthesis or commas. See below for an example.
The macro (really a Python lambda) should return either a String or an
List of Strings. The string in both cases is a debugger command. Each
string gets tokenized by a simple split() . Note that macro processing
is done right after splitting on ;;. As a result, if the macro
returns a string containing ;; this will not be interpreted as
separating debugger commands.
If a list of strings is returned, then the first string is shifted from
the list and executed. The remaining strings are pushed onto the command
queue. In contrast to the first string, subsequent strings can contain
other macros. ;; in those strings will be split into separate
commands.
Here is an trivial example. The below creates a macro called l=
which is the same thing as list .:
macro l= lambda: 'list .'
A simple text to text substitution of one command was all that was needed here. But usually you will want to run several commands. So those have to be wrapped up into a list.
The below creates a macro called fin+ which issues two commands
finish followed by step:
macro fin+ lambda: ['finish','step']
If you wanted to parameterize the argument of the finish command you
could do that this way:
macro fin+ lambda levels: ['finish %s' % levels ,'step']
Invoking with:
fin+ 3
would expand to: ['finish 3', 'step']
If you were to add another parameter for step, the note that the
invocation might be:
fin+ 3 2
rather than fin+(3,2) or fin+ 3, 2.
See also alias, and info macro.
setautoeval [on|off]
Evaluate unrecognized debugger commands.
Often inside the debugger, one would like to be able to run arbitrary
Python commands without having to preface Python expressions with
print or eval. Setting autoeval on will cause unrecognized
debugger commands to be eval'd as a Python expression.
Note that if this is set, on error the message shown on type a bad debugger command changes from:
Undefined command: "fdafds". Try "help".
to something more Python-eval-specific such as:
NameError: name 'fdafds' is not defined
One other thing that trips people up is when setting autoeval is that there are some short debugger commands that sometimes one wants to use as a variable, such as in an assignment statement. For example:
s = 5
which produces when autoeval is on:
Command 'step' can take at most 1 argument(s); got 2.
because by default, s is an alias for the debugger step command.
It is possible to remove that alias if this causes constant problem.
setautolist [on|off]
Run the list command every time you stop in the debugger. With this, you will get output like:
-> 1 from subprocess import Popen, PIPE (trepan2) next (/users/fbicknel/Projects/disk_setup/sqlplus.py:2): <module> -- 2 import os 1 from subprocess import Popen, PIPE 2 -> import os 3 import re 4 5 class SqlPlusExecutor(object): 6 def __init__(self, connection_string='/ as sysdba', sid=None): 7 self.__connection_string = connection_string 8 self.session = None 9 self.stdout = None 10 self.stderr = None (trepan2) next (/users/fbicknel/Projects/disk_setup/sqlplus.py:3): <module> -- 3 import re 1 from subprocess import Popen, PIPE 2 import os 3 -> import re 4 5 class SqlPlusExecutor(object): 6 def __init__(self, connection_string='/ as sysdba', sid=None): 7 self.__connection_string = connection_string 8 self.session = None 9 self.stdout = None 10 self.stderr = None (trepan2)
You may also want to put this this in your debugger startup file. See [#Startup_Profile]
python [-d]
Run Python as a command subshell. The sys.ps1 prompt will be set to
trepan2 >>>.
If -d is passed, you can access debugger state via local variable debugger.
To issue a debugger command use function dbgr(). For example:
dbgr('info program')
Set consecutive stops must be on different file/line positions.
By default, the debugger traces all events possible including line, exceptions, call and return events. Just this alone may mean that for any given source line several consecutive stops at a given line may occur. Independent of this, Python allows one to put several commands in a single source line of code. When a programmer does this, it might be because the programmer thinks of the line as one unit.
One of the challenges of debugging is getting the granualarity of stepping comfortable. Because of the above, stepping all events can often be too fine-grained and annoying. By setting different on you can set a more coarse-level of stepping which often still is small enough that you won't miss anything important.
Note that the 'step' and 'next' debugger commands have '+' and '-' suffixes if you wan to override this setting on a per-command basis.
See also set trace to change what events you want to filter.
disassemble [thing] [start-line [end-line]]
With no argument, disassemble the current frame. With an integer start-line, the disassembly is narrowed to show lines starting at that line number or later; with an end-line number, disassembly stops when the next line would be greater than that or the end of the code is hit.
If start-line or end-line is., +, or -, the current
line number is used. If instead it starts with a plus or minus prefix to
a number, then the line number is relative to the current frame number.
With a class, method, function, pyc-file, code or string argument disassemble that.
Examples:
disassemble # Possibly lots of stuff dissassembled disassemble . # Disassemble lines starting at current stopping point. disassemble + # Same as above disassemble +0 # Same as above disassemble os.path # Disassemble all of os.path disassemble os.path.normcase # Disaassemble just method os.path.normcase disassemble -3 # Disassemble subtracting 3 from the current line number disassemble +3 # Disassemble adding 3 from the current line number disassemble 3 # Disassemble starting from line 3 disassemble 3 10 # Disassemble lines 3 to 10 disassemble myprog.pyc # Disassemble file myprog.pyc