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Full Discussion: Subtracting Variables which are commands
Top Forums UNIX for Dummies Questions & Answers Subtracting Variables which are commands Post 1771 by PxT on Thursday 29th of March 2001 10:55:10 AM
Old 03-29-2001
This gets tricky because what if their login time is 2:59, and the logout time is 3:10. 3:10-2:59=? The shell doesn't know that you are trying to subtract times, it just sees numbers with a colon in the middle. A better way to do this might be to use the 'last' command, as one of the fields it provides is the total log in time.
 

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LEARN ABOUT OSF1

ac

ac(8)							      System Manager's Manual							     ac(8)

NAME

       ac - Outputs connect-session records

SYNOPSIS

       ac [-dp] [-w filename] [user(s) ...]

FLAGS

       Outputs the total connect time for each midnight-to-midnight period for which a wtmp file exists. When user(s) is specified, this flag lim-
       its the output to the login names specified by any user(s) parameter(s).  Outputs the connect time total by individual login  name  of  the
       user  specified	with  the -p flag and the user(s) parameter.  Omission of this flag permits a total only for the midnight-to-midnight time
       period for all logged in users to be produced.  Specifies a wtmp file other than the /var/adm/wtmp file.  The wtmp file you access for data
       may  have  been created automatically by some shell script administration command (for example, runacct) or manually by the system adminis-
       trator when the original /var/adm/wtmp file becomes too large.

DESCRIPTION

       The ac command prints to the default output device the total connect time in hours to the nearest hundredth for all users, or  the  connect
       time  for  any  user(s) specified with the -p flag. It also prints the names of users specified by the user(s) parameter who have logged in
       during the life of the current /var/adm/wtmp file.

       Connect-time records are written by the init and the login programs and are collected in the /var/adm/wtmp file, when such a  file  exists.
       When  a	/var/adm/wtmp  file  does  not	exist, no connect-time accounting records are written; consequently, when connect-time records are
       wanted, the system administrator should create a /var/adm/wtmp file that has an initial record length of 0 (zero). Records  in  wtmp  files
       (there may be more than one such file) should be processed periodically to keep the files from becoming too large.

       When  you  use  the  runacct  command  in a shell script, additional wtmp files can be automatically created whenever the current wtmp file
       becomes too large. You can output the contents of any of these other files when you specify the -w flag and the desired wtmp filename.

       The ac command is run independently with respect to any accounting shell procedure created or run by any of the acct/* shell procedures	or
       runacct commands.

EXAMPLES

       To obtain an output of the total connect time for all users who have logged in during the life of the current wtmp data file, enter:

	      /usr/sbin/ac  To	obtain	an  output of the total connect time for grossman and mcwhinney as recorded in the default wtmp data file,
	      enter:

	      /usr/sbin/ac  grossman  mcwhinney To obtain an output of the connect time subtotals for grossman and mcwhinney as  recorded  in  the
	      default wtmp data file, enter:

	      /usr/sbin/ac -p  grossman  mcwhinney

FILES

       Specifies the command path.  Is the active data file for the collection of connect-time records.

RELATED INFORMATION

       Commands:  login(1), init(8) delim off

																	     ac(8)
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