To get process name OR command name using process id.

For example I want to find out the command name or process name for the process id 16874 

>> ps ax -o pid,cmd | grep 16874 | grep -v grep | cut -d " " -f2-

               1                           2                 3                 4

output : 

>> /usr/local/bin/perl -w /home/y/bin/yroot hdfs_proxy --user dkuldeep

Explanation:    

1) To get the list of PIDs and relevant commands:

>> ps ax -o pid,cmd  

>>

PID CMD

    1 init [3]

    2 [migration/0]

    3 [ksoftirqd/0]

    4 [migration/1]

    5 [ksoftirqd/1]

    6 [events/0]

    7 [events/1]

    8 [khelper]

    9 [kacpid]

   33 [kblockd/0]

   2465 /usr/sbin/snmpd -u nobody -g nobody -I -smux -Lsd -Lf /dev/null -p /var/run/snmpd.pid

   2511 /usr/sbin/automount --timeout=600 /mnt file /etc/auto.mnt

   2525 /usr/sbin/smartd

   2534 /usr/sbin/acpid

   2552 /usr/sbin/sshd-2222 -f /etc/ssh/sshd_config.2222

   16874 /usr/local/bin/perl -w /home/y/bin/yroot hdfs_proxy --user dkuldeep

2) To filter for required PID (16874)

>>ps ax -o pid,cmd | grep 16874

>>

552 grep 16874

16874 /usr/local/bin/perl -w /home/y/bin/yroot hdfs_proxy --user dkuldeep

3)  To remove the grep command line

>> ps ax -o pid,cmd | grep 16874 | grep -v grep 

>>

16874 /usr/local/bin/perl -w /home/y/bin/yroot hdfs_proxy --user dkuldeep

4) To extract the exact command line

>> ps ax -o pid,cmd | grep 16874 | grep -v grep | cut -d " " -f2-

>>
/usr/local/bin/perl -w /home/y/bin/yroot hdfs_proxy --user dkuldeep