[SOLVED] Help with the last command

omicky83 · 10-02-2013, 06:16 AM

I'm new to scripting and wondered if I could get a little help. I would like to execute a script that will extract or display the past 7 days of login after issuing the "last" command

Linux OS used Redhat 4.

pan64 · 10-02-2013, 06:35 AM

is this your homework?
what have you done so far?

colucix · 10-02-2013, 06:37 AM

Well, first you have to determine the last day in the past you want to be printed out:

Code:

last_day=$(date -d "8 days ago" +"%a %b %e")

then you can parse the ouput of the last command using awk:

Code:

last | awk -v day="$last_day" '$0 ~ day {x = 1} !x'

However, this solution assumes there is at least one entry per day in the wtmp file. A more general solution is to parse the date in every line of the output and check if it is more than 7 days ago:

Code:

#!/bin/bash
while read line
do
  day=${line:39:10}
  if [[ $(( $(date -d "today 00:00:00" +%s) - $(date -d "$day" +%s) )) -le 604800 ]]
  then
    echo "$line"
  else
    break
  fi
done < <(last)

Hope this helps.

omicky83 · 10-02-2013, 06:44 AM

Quote:

Originally Posted by pan64

is this your homework?
what have you done so far?

Hello Pan

I know i can use the last command

last |grep date -d -7days

omicky83 · 10-02-2013, 06:46 AM

Thanks Colucix. Trying it out.

Mike

omicky83 · 10-02-2013, 07:01 AM

Hello Colucix

I get this error when i try to run the batch script given.

mike.sh: line 5: syntax error in conditional expression
'ike.sh: line 5: syntax error near `]]

Thanks

Michael.

colucix · 10-02-2013, 07:24 AM

Strange, it works for me using bash version:

Code:

$ bash --version
GNU bash, version 4.2.42(1)-release (i586-suse-linux-gnu)
Copyright (C) 2011 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

What version of bash have you got? Also, please show us the current version of your script using CODE tags to preserve indentation. To use CODE tags you can put [CODE] and [/CODE] before and after the lines of code, respectively.

omicky83 · 10-02-2013, 07:29 AM

Content of mike.sh file.

Code:

#!/bin/bash
while read line
do
  day=${line:39:10}
  if [[ $(( $(date -d "today 00:00:00" +%s) - $(date -d "$day" +%s) )) -le 604800 ]]
  then
    echo "$line"
  else
    break
  fi
done < <(last)

Details of my bash file

GNU bash, version 3.2.25(1)-release (x86_64-redhat-linux-gnu)
Copyright (C) 2005 Free Software Foundation, Inc.

---------- Post added 10-02-13 at 07:30 AM ----------

Can i get your skype details please ? I think it will be easier to work with you there.

Mike

colucix · 10-02-2013, 07:37 AM

I tried your/mine code on a machine with the same bash version as yours

Code:

GNU bash, version 3.2.25(1)-release (x86_64-redhat-linux-gnu)
Copyright (C) 2005 Free Software Foundation, Inc.

and it works. At this point I have no clue. Maybe try to change the code?

Edit: I have no skype account, but in the spirit of the LQ community better to share the discussion for the benefit of others having similar problems!

colucix · 10-02-2013, 07:56 AM

What if you try to use single square brackets instead of double square brackets in the if/then construct?

Another one could be:

Code:

#!/bin/bash
day_last=$(date -d "7 days ago 00:00:00" +%s)
while read line
do
  day_now=${line:39:10}
  day_now=$(date -d "$day_now" +%s)
  if [[ $day_now -ge $day_last ]]
  then
    echo "$line"
  else
    break
  fi
done < <(last)

omicky83 · 10-02-2013, 08:07 AM

Code:

#!/bin/bash
day_last=$(date -d "7 days ago 00:00:00" +%s)
while read line
do
  day_now=${line:39:10}
  day_now=$(date -d "$day_now" +%s)
  if [[ $day_now -ge $day_last ]]
  then
    echo "$line"
  else
    break
  fi
done < <(last)

Output when i try to run this

mike.sh: line 7: syntax error in conditional expression
'ike.sh: line 7: syntax error near `]]
'ike.sh: line 7: ` if [[ $day_now -ge $day_last ]]

Can you paste your output here please ?

Michael.

colucix · 10-02-2013, 08:11 AM

Please try without double brackets:

Code:

#!/bin/bash
day_last=$(date -d "7 days ago 00:00:00" +%s)
while read line
do
  day_now=${line:39:10}
  day_now=$(date -d "$day_now" +%s)
  if [ $day_now -ge $day_last ]
  then
    echo "$line"
  else
    break
  fi
done < <(last)

My output is exactly what is supposed to be: the first N lines of the output of the last command until Wed Sep 25.

omicky83 · 10-02-2013, 08:19 AM

Code:

#!/bin/bash
day_last=$(date -d "7 days ago 00:00:00" +%s)
while read line
do
  day_now=${line:39:10}
  day_now=$(date -d "$day_now" +%s)
  if [ $day_now -ge $day_last ]
  then
    echo "$line"
  else
    break
  fi
done < <(last)

We are making progress here .

Please find the output below

Code:

bash mike.sh
mike.sh: line 13: syntax error near unexpected token `done'
'ike.sh: line 13: `done < <(last)

colucix · 10-02-2013, 08:30 AM

Ok. It looks like you are running the bash shell in compatibility mode with the old /bin/sh, that lacks the [[ command and the process substitution. Try this now, it should work:

Code:

#!/bin/bash
day_last=$(date -d "7 days ago 00:00:00" +%s)
last | while read line
do
  day_now=${line:39:10}
  day_now=$(date -d "$day_now" +%s)
  if [[ $day_now -ge $day_last ]]
  then
    echo "$line"
  else
    break
  fi
done

Anyway, I'm curious at this point about the shell version. Please show us the output of the following three commands

Code:

ls -l /bin/bash
file /bin/bash
alias bash

and please, use CODE tags!

colucix · 10-02-2013, 08:35 AM

Code:

bash mike.sh
mike.sh: line 13: syntax error near unexpected token `done'
'ike.sh: line 13: `done < <(last)

Another clue: I noticed the name of the script in the error message lacks the initial "m". I suspect at this point that there is a problem of format: maybe are you writing these script on a windows machine? If this is the case, take in mind that Windows and Unix/Linux have different line terminators and the windows terminator \r\n (that is Carriage Return + Newline) often triggers weird errors in bash.

Please try to write down your script in linux or use the dos2unix command to convert it to Unix format:

Code:

dos2unix mike.sh

then run again (any version of the scripts posted above).