Sunday, 29 January 2012

ps


ps
ps   displays  all the processes  in a unix   system. every command, script or an application is considered as a process in unix. All the processes run until the command or application is completed or stopped. Each process has a unique process id ( PID)
It has the same output of windows tasklist command.
Example 1)
to list  only your processes  (i:e all the commands , and applications run in current  session )
/home/priya$ ps
   PID       TTY      TIME   CMD
  217140  pts/2  0:00 -ksh
  594062  pts/2  0:00 -ksh
  652138  pts/2  2:03  java   webfile.java
  820120  pts/2  0:00  ps


Example 2)
To  list  all  the processes running  in  the server  page wise , use –ef option
/home/priya$  ps  -ef  | pg
 UID     PID       PPID C    STIME    TTY  TIME   CMD
priya  184434       1  24 05:32:34      -  0:50 java  /usr/bin/java/start-web.java
root   213146       1   0 05:32:31      -  1:21 java  /usr/bin/dsmc
matt   327814  893836   0 12:28:09      -  0:00 sleep 120
root   352266       1   0 05:32:38      -  0:14 java  /usr/bin/ftpd  
priya  368734       1   0 05:32:42      -  0:07
priya  372912       1   0 05:32:43      -  0:10 java  /usr/bin/java/start-web3.java
scripts 409806       1  0 05:32:39      -  0:13 java  /usr/bin/java/start-web2.java -d final -f clear
scripts  418030       1   0 05:32:35      -  1:08 java  /usr/bin/java/start-web.java -d final -f clear
scripts  430084       1   0 05:32:23      -  0:02 /usr/bin/perl -w getfile.cgi
scripts  442592  430084   0 12:17:38      -  0:00 sleep 900
scripts  454810       1   3 05:32:29      -  1:42 java  /usr/bin/java/start-web.java -d final -f clear
standard input

Example 3)
To list all the processes which are run by an user,
/home/priya$  ps  -fu   matt
UID     PID    PPID   C    STIME     TTY    TIME CMD
matt  174431       1  24 05:32:34      -        0:50 wc -l
matt  723156       1   0    05:32:31     pts/2 1:21 cat items
matt  327814  893836   0 12:28:09      -   0:00 sleep 120
matt    1566          1   0 0 5:32:38  pts/1    0:14 sed ‘s/sim//’
matt  668739       1   0 05:32:42      -          0:07 /usr/bin/perl
matt  352912       1   0 05:32:43      -          0:10 java hello.java


All your processes and  the processes  of other users can be viewed.

In the output of the command above ,the various column heads are defined as follows.
PID
The process ID of the process.


UID
The user ID of the process owner. The login name is printed under the -f flag.

PPID
The process ID of the parent process.

    C
CPU utilization of process or thread, incremented each time the system clock ticks and the process or thread is found to be running. Large values indicate a CPU intensive process and result in lower process priority whereas small values  indicate an I/O intensive process and result in a more favourable priority.


STIME
The starting time of the process.

TTY
The controlling terminal for the process
if There is a ‘-‘ ,it means the  process is not associated with a terminal.
Otherwise indicates The TTY number. For example, the entry pts/2 indicates terminal 2.

CMD
Contains the command name which started the process. The full command name and its parameters are displayed with the -f flag.

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