debug cheatsheet

From http://www.scribd.com/doc/23548865/Debugging-Ruby

lsof
list open files
lsof -nPp <pid>

-n
Inhibits the conversion of network numbers to host names for 
network files.
-P
Inhibits the conversion of port numbers to port names for network 
files


strace
trace system calls and signals
strace -cp <pid>

-c 
Count time, calls, and errors for each system call and report a summary on program exit.
-p pid 
Attach to the process with the process ID pid and begin tracing.

strace -ttTp <pid> -o <file>

-t 
Prefix each line of the trace with the time of day.
-tt 
If given twice, the time printed will include the microseconds.
-T 
Show the time spent in system calls. This records the time difference between the beginning and the end of each system call.
-o filename 
Write the trace output to the file filename rather than to stderr.

tcpdump
dump traffic on a network
tcpdump -i eth1 -s 1500 -nqA tcp dst port 80
tcpdump -i eth0 -s 1500 -nqA tcp dst port 3306
tcpdump -i eth1 -s 1500 -w <file> tcp dst port 80

-i <eth> 
Network interface.
-s <len> 
Snarf len bytes of data from each packet.
-n 
Don't convert addresses (host addresses, port numbers) to names.
-q 
Quiet output. Print less protocol information.
-A 
Print each packet (minus its link level header) in ASCII.
-w <file> 
Write the raw packets to file rather than printing them out.
<expr> 
libpcap expression, for example:
  tcp src port 80 
  tcp dst port 3306
  
  
google-perftools
Google’s CPU profiler
pprof ./myapp /tmp/myprof


ltrace
trace library calls
ltrace -cp <pid> ltrace -ttTp <pid> -o <file>


ltrace/libdl (http://github.com/ice799/ltrace/tree/libdl)
trace dlopen’d library calls
ltrace -F <conf> -bg -x <symbol> -p <pid>

-b 
Ignore signals.
-g 
Ignore libraries linked at compile time.
-F <conf> 
Read prototypes from config file.
-x <sym> 
Trace calls to the function sym.
-s <num> 
Show first num bytes of string args.

gdb
the GNU debugger
gdb <program> gdb <program> <pid>


perftools.rb (http://github.com/tmm1/perftools.rb)
google-perftools for ruby


gdb.rb (http://github.com/tmm1/gdb.rb)
gdb with MRI hooks
gdb.rb <pid>


bleak_house (http://github.com/fauna/bleak_house)
ruby memory leak detector