Script runs as root but not as crontab? or
Why does my script run as the root user but won't run from cron.daily? or
What user does cron.daily run as?

I recently ran into a problem with a Subversion update script I wished to execute daily. Unfortunately the svn update failed due to a permissions error. This made little sense to me as I believed if I ran the script as root the script should work. It turns out that on some *nix systems (RH Linux and other variants) the root user has a home directory called /root. Within this directory is where the .subversion directory sits which contains your connection information.  Thus solution was to set the HOME variable in my script, as crontab doesn't necessarily pick up environment variables that you get when you log in.

Below you will find the simple fix.


#!/bin/sh
HOME=/root
export HOME=${HOME}
cd /usr/local/svn_workspace/trunk
/opt/CollabNet_Subversion/bin/svn update

Shell Script Timestamps

Shell Script Trick No. 3 Timestamps
Over the years I've had the need to use time stamps in my scripts to name log files or directories. I created this function to make the task easier.
Usage is as follows:
timestamp "yyyymmdd"
sets the variable $timestamp to 20120818

timestamp "mm/dd/yy"
sets the varible $timestamp to 08/18/2012


##################
# timestamp: This function generates a timestamp
# Calling Profile: timestamp "format"
# Returns:  timestamp
##################
timestamp () {
  format=$1
    yyyy=`date +%Y`
    yy=`date +%y`
    month=`date +%m`
    day=`date +%d`
    hour=`date +%H`
    min=`date +%M`
    sec=`date +%S`

case $format in
     "yesterday yyyy.mm.dd" ) timestamp=`date --date yesterday "+%Y.%m.%d"` ;;
     "yesterday yyyy-mm-dd" ) timestamp=`date --date yesterday "+%Y-%m-%d"` ;;
     "yesterday yyyymmdd" )   timestamp=`date --date yesterday "+%Y%m%d"` ;;
     "yyyy" )                 timestamp="$yyyy" ;;
     "yy" )                   timestamp="$yy" ;;
     "dd" )                   timestamp="$day" ;;
     "mm" )                   timestamp="$month" ;;
     "hh:mm:ss" )             timestamp="$hour:$min:$sec" ;;
     "hhmmss" )               timestamp="$hour$min$sec" ;;
     "mm/dd/yy" )             timestamp="$month/$day/$yy" ;;
     "mm/dd/yyyy" )           timestamp="$month/$day/$yyyy" ;;
     "yyyymmdd"    )          timestamp="$yyyy$month$day" ;;
     "yyyymmddhhmm" )         timestamp="$yyyy$month$day$hour$min" ;;
     "yyyymmddhhmmss" )       timestamp="$yyyy$month$day$hour$min$sec" ;;
     "yyyy-mm-dd" )           timestamp="$yyyy-$month-$day" ;;
     "yyyy.mm.dd" )           timestamp="$yyyy.$month.$day" ;;
     "mmddyyyy"   )           timestamp="$month$day$yyyy" ;;
     "dd/mm/yy"   )           timestamp="$day/$month/$yy" ;;
     "dd-mm-yy"   )           timestamp="$day-$month-$yy" ;;
     "dd-mm-yyyy" )           timestamp="$day-$month-$yyyy" ;;
     "mm-dd-yy"   )           timestamp="$month-$day-$yy" ;;
     "mm-dd-yyyy" )           timestamp="$month-$day-$yyyy" ;;
     "mm dd, yyyy" )          timestamp="$month $day, $yyyy" ;;
             *   )            timestamp="$hour$min$sec";;
esac 
}

Shell script reading files

Shell Script Trick No. 2
Reading files. Over the years I have used a couple of different methods for reading configuration files.
I present the two I have used the most with the second being my current favorite.

cat config | while read line
do
LINE=`echo $line | cut -d: -f2`
if [ "$LINE" = "#" ];then
  echo 
else
  echo "$LINE:\c"
fi
done

#The read command eats leading spaces
exec <  ${datafile}
while read line  
do
 # Don't process lines with comments just skip them. 
 if ( echo $line | grep "^#" > /dev/null 2>&1 );then
   continue
 fi
done

Remove Carriage Return from string variable

Recently I was tasked with writing some scripts to copy log files from a drop site to a working directory then to unzip them. This was not a very difficult task but I ran into a small issue, how to remove a carriage return from a string variable

How to remove a Carriage Return from a string variable?

     #setup     

     logs=`ls`

     #use the tr command and the octal code for CR

     logs=`echo ${logs} | tr -d '\15'`