CODEWITHSUNDEEP
shellunix
Lovika
Lovika

Reputation: 617

what ps -e -o user:20, pid means?

I have a already written script which has this line PID = ps -e -o user:20,pid,cmd

Could anybody explain me the meaning of this line? I am bit confused with user:20 part

Thanks!

Upvotes: 0

Views: 1766

Answers (3)

JDGuide
JDGuide

Reputation: 6525

ps - This command report a snapshot of the current processes.

-e , This options helps to select all processes.Identical to -A.

-o , This options helps to specify user-defined format.

user:20 , This will help to format the output of ps command.The user:20 will add some extra 20 space character betweens the columns. Below the example will help you to find the difference.

jdeveloper@jdeveloper ~ $ ps -e -o user:20,pid
    USER                   PID
    root                  2926
    jdeveloper            2948
    root                  3255
    root                  3570
    root                  3802
    jdeveloper            3825
    jdeveloper            3860

Now , lets try with 10 character space padding in response.

jdeveloper@jdeveloper ~ $ ps -e -o user:10,pid
USER         PID
root        2926
jdeveloper  2948
root        3255
root        3570
root        3802
jdeveloper  3825
jdeveloper  3863

Find more about ps command using man command.Try 

jdeveloper@jdeveloper ~ $ man ps

Hope it will help you.

Upvotes: 0

Ben
Ben

Reputation: 410

From ps's man page:

   -o format
          User-defined format.  format is a single argument in the form of a blank-separated or comma-separated list, which offers a way to specify
          individual output columns.  The recognized keywords are described in the STANDARD FORMAT SPECIFIERS section below.  Headers may be renamed (ps
          -o pid,ruser=RealUser -o comm=Command) as desired.  If all column headers are empty (ps -o pid= -o comm=) then the header line will not be
          output.  Column width will increase as needed for wide headers; this may be used to widen up columns such as WCHAN (ps -o pid,wchan=WIDE-
          WCHAN-COLUMN -o comm).  Explicit width control (ps opid,wchan:42,cmd) is offered too.  The behavior of ps -o pid=X,comm=Y varies with
          personality; output may be one column named "X,comm=Y" or two columns named "X" and "Y".  Use multiple -o options when in doubt.  Use the
          PS_FORMAT environment variable to specify a default as desired; DefSysV and DefBSD are macros that may be used to choose the default UNIX or
          BSD columns.

Explicit width control (ps opid,wchan:42,cmd) is offered too.

So you'll get a user column with 20-char's width.

Upvotes: 1

user8549610
user8549610

Reputation:

ps is a command name used to show processes running in the system currently.

-e is a "short" option which means that all processes should be listed.

-o user:20,pid,cmd is an option which sets expected format of lines to be printed on screen, i.e. we want the first column to contain usernames (who own the processes) padded to 20 characters, the second column to show process IDs and the third column to contain command names which have been used to start the processes. Just that.

Also, you can simply try to run this yourself in your terminal: ps -e -o user:20,pid,cmd and see what happens.

Upvotes: 2

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