unix

# how to strace a process -- also filters strace's output with grep
# PID is 30713 and max string size to output is 33k
$ sudo strace -p 30713 -f -s 33000 2>&1 | grep 'date range'

# how to figure out which hostname/port a running python process is connected to mysql on
$ ps aux | grep py.test
ubuntu   23668  4.8 12.7 611332 491252 pts/2   S+   22:26   3:40 /usr/bin/python /usr/local/bin/py.test -s -v -m memcache_test

$ strace -p 23668
write(6, "in_id=5279)) AND  NOT (brand_id="..., 34867) = 34867

$ ls -l /proc/23668/fd
lrwx------ 1 ubuntu ubuntu 64 2013-04-08 23:18 0 -> /dev/pts/2
lrwx------ 1 ubuntu ubuntu 64 2013-04-08 23:18 1 -> /dev/pts/2
lrwx------ 1 ubuntu ubuntu 64 2013-04-08 22:44 2 -> /dev/pts/2
lrwx------ 1 ubuntu ubuntu 64 2013-04-08 23:18 3 -> /dev/pts/2
lrwx------ 1 ubuntu ubuntu 64 2013-04-08 23:18 4 -> socket:[11322298]
lrwx------ 1 ubuntu ubuntu 64 2013-04-08 23:18 5 -> socket:[11322301]
lrwx------ 1 ubuntu ubuntu 64 2013-04-08 23:18 6 -> socket:[11322305]
lrwx------ 1 ubuntu ubuntu 64 2013-04-08 23:18 7 -> socket:[11322308]


$ netstat -p -e -e | grep 23668
tcp        0      0 localhost:42373         localhost:3308          ESTABLISHED ubuntu     11322305    23668/python
tcp        0      0 ip-10-202-67-19.e:57630 domU-12-31-38-04-:11211 ESTABLISHED ubuntu     11322308    23668/python
tcp        0      0 localhost:47805         localhost:3307          ESTABLISHED ubuntu     11322298    23668/python
tcp        0      0 ip-10-202-67-19.e:51021 domU-12-31-39-14-:mysql ESTABLISHED ubuntu     11322301    23668/python

# sed examples
sudo sed -i 's/^-l 127.0.0.1$/-l 0.0.0.0/' /etc/memcached.conf

# determine which device/mount-point a file or directory exists on
$ df $FILENAME | awk 'NR==1 {next} {print $6; exit}'
$ df -h