Tips n' Tricks

One has taken a photograph with a digital camera, downloaded the JPEG image onto an MSwindows system, modified the image using PhotoShop or similar utility and then discovered that the time setting of one's camera was 7min 50secs slow. Having transferred the file to a linux system, one now wants to set the modification time of the file, i.e. the time normally shown with the ls -l command, via the touch command to correspond to the time at which the photograph was originally taken.

To help understand the example, here is a description of my empirical observations about JPEG images, at least those from a Sony DSC-T?? camera. The command:

      strings  | grep 2007
    

      2007:mm:dd hh:mm:ss
    

     function getDate () {
       if [ $# != 1 ]; then echo Usage: getDate \<jpeg-file\>; return 1; fi
       strings $1 | grep 2007 > /dev/null
       if [ $? != 0 ]; then echo No date found in JPEG file.; return 1; fi
       strings $1 | awk -F: '          # Specify a colon as the field separator
         /2007/{x++;                   # Count the number of records found
                                       # containing "2007"
              if (x == 2) {            # Process the second such record.
                                       #   $1 is the year
                                       #   $2 is the month
                                       #   $3 is the day and hour: "dd hh"
                                       #   $4 is the minutes
                                       #   $5 is the seconds.
                split ($3, DDHH, " "); # The Day/Hour field needs to be split. 
                DD = DDHH[1];
                HH = DDHH[2]; 
                MM = $4+7;                   # Add 7 minutes and 
                SS = $5+50;                  # 50 seconds.
                if (SS > 59) {MM++; SS-=60}; # Correct for overflow of seconds and
                if (MM > 59) {HH++; MM-=60}; # minutes, but ignore day overflows.
                printf "%s-%s-%02d %02d:%02d:%02d\n", $1, $2, DD, HH, MM, SS;
              }
         }
       '
     }

     function reTouch () {
       if [ $# == 0 ]; then echo Usage: reTouch \<jpeg-file\> ...; return 1; fi
       for jpg do
         if [ -e $jpg ]; then
           echo Processing $jpg ...
           newDate="$(getDate $jpg)"
           if [ $? = 0 ]; then
             touch -d "$newDate" $jpg
           else
             echo "      " No date found in $jpg
           fi
         else
           echo "      " $jpg not found.
         fi
       done
     }
  

• To Make a Window Sticky Automatically
  Under the Another Level window manager, it is possible to cause a window to be sticky when it is created by means of a resource file. The file used to do this is:
  
        /etc/X11/AnotherLevel/fvwm2rc.defstyles.m4
  
  As an example, the SLS launcher window is made sticky automatically via a record of the form:
  
        Style  "launcher.tcl*"  Sticky
  
  Maybe it is possible to have a local copy of this file which will override the file in /etc/X11/AnotherLevel. Maybe http://www.poulpetersen.dk/linux/ukfvwm.htm is a useful starting point for more information.

Under the Gnome desktop, several window managers are available. The one most commonly configured at SLS is Enlightenment, to which the following notes apply.

• To Make a Window Sticky
  To flip a window's sticky property between sticky and not-sticky under the Enlightenment window manager, pop-up the menu under the top-left square of the window's banner, drag the cursor to the Stick/Unstick item and release the mouse.

• To Change a Window's Stacking Order
  A window's stacking order is changed using the same pop-up menu as is used to change the window's stickiness. In this case, drag the cursor to the item labelled Set Stacking, enter the sub-menu and release the mouse on the desired stacking level, viz. Below, Normal, Above or On Top.

• To Make a Window Sticky Automatically
  To make a window automatically sticky when it is created under the Enlightenment window manager, create the window, make it sticky (and modify its other attributes, if so desired) as described above and then pop-up the menu under the top-left square of the window's banner. By following the sub-menu Remember State to All Attributes (or one of the other items, if more appropriate), it is possible to cause the window manager to remember the window's attributes. Presumably this information is saved in a resource file somewhere. If anyone discovers which one it is and how, please send me a note about it.

• To Make a Window Sticky Automatically
  Under the KDE window manager, one can set a so-called Filter using the "KDE Control Center" and following the menus Window Behavior (sic ... why on earth can't Americans learn to spell!) --> Advanced --> Filters. There is then a GUI which enables one to set matching patterns for window names and to specify the attributes of windows so selected.

  This GUI would appear to update the resource file, ~/.kde/share/config/kwmrc.

The standard man pages are stored in gzip formatted files under directory /usr/man/man<n>, where <n> is the manual page section number.

As an example, the following command will generate a file in PostScript format of the bash manual page, which is in Section 1 of the man pages:

        gunzip -c /usr/man/man1/bash.1.gz   |   \
              groff -Tps -man   >   bash.ps

The following command allows one to send email from the SLSnet, for example, and make it look as though it came from you:

cat <file>   |   mail   -s "<subject>"   <to>   ...   --   -f   <from>

vi   /tmp/mail.txt
cat /tmp/mail.txt   |   mail   -s "A test email"   sls-controls@psi.ch \

--   -f   david.maden@psi.ch