[clug] incrementing time

Stephen Jenkin sjenkin at pcug.org.au
Thu Nov 6 00:18:55 EST 2003

Boris et al,

Here's a little bash script that will check a number of files and call a
command on files older than xxx seconds...

Uses: '-ot' in test.
[ file1 -ot file2 ] ==> true if file1 older than file2

and the GNU touch, '-B secs' ==> backwards some seconds.
For portability, It is possible to use something like:
touch `TZ=xxx-10yyy date +%M%D%H%M`
but fooling around with the TZ variable and coping with daylight saving is
really painful.  Look at zdump output for Australia/B=NSW: There is EST & 
EST!! Standard time and Summer time.  To tell in a script [date +%Z] if
it's summer time or not, requires building a new timezone [found zic but
not the input file] with a different name for summer time. 
In the US EST/EDT is used.

Here is example output of date with TZ changed:
[@cdr root]# date
Thu Nov  6 00:10:49 EST 2003
[@cdr root]# date +%m%d%H%M
[@cdr root]# TZ=xxx-10 date +%m%d%H%M  ((in not-summer, use -9))

OK, time for the script.  A few options as leads...
Hope this long expo was useful :-)

# /stevej/bin/chk_file
# Steve Jenkin Wed Nov  5 23:15:52 EST 2003

PRG=`basename $0`

trap "rm $tmpfile" EXIT


while getopts ':B:c:xisv' opt
    case $opt in
    B ) back=$OPTARG ;;
    c ) cmd="$OPTARG" ;;
    x ) set -x ;;
    i ) invert=1 ;;
    s ) verbose=0 ;;
    v ) verbose=1 ;;
    * ) echo "$OPTARG Not recognised" >&2; exit 1 ;;
shift $(( $OPTIND - 1 ))

touch -B $back $tmpfile

for file in "$@"
    if [[ "$file" -ot $tmpfile ]]
        if [[ $invert -eq 0 ]] && [[ -n "$cmd" ]]
            $cmd "$file"
            [[ $verbose -eq 1 ]] && echo "${file}: older"
        if [[ $invert -ne 0 ]] && [[ -n "$cmd" ]]
            $cmd "$file"
            [[ $verbose -eq 1 ]] && echo "${file}: newer or same"


Steve Jenkin, Unix Sys Admin
0412 786 915 (+61 412 786 915)
PO Box 48, Kippax ACT 2615, AUSTRALIA

On Wed, 5 Nov 2003, Rousak, Boris wrote:

> Greeting all,
> This is a bit basic but I am having a mind blank :). I am trying to write a
> script that will check a time stamp written in a file to see if it has been
> an hour since it was made. The stamp is in a format, Nov 03 07:32:06. I am
> using Ksh and the only way possible that I could find (google and all) is to
> convert the date to time since 1970 and do a number comparison. This is
> however a hassle, so the question is: can anyone suggest an easier way to do
> this, awk maybe or something to that effect. I have looked at perl, but that
> requires an extra module download, namely: Date::Manip and this is not an
> option for me. If anyone can hit me with a clue-bat that would be much
> appreciated.
> Regards,
> Boris
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