wget concurrent execution!!!

[unix81]

Hi,
Im using wget to retrieve information via ftp every 2 hours from a server ( using UNIX crontab command). I´d like to know what will happen if the next wget executes while the other is still mirroring data. How can I avoid any possible error?

Thats all, hope somebody can help me

 

[marsd]

Look for a wget pid and hold off till the original finishes
with a script internal max timeout value for error is my best guess.

Not too hard.
If you need an example write back.

 

[unix81]

thanks marsk , thats what i was thinking but i´d really appreciate if you could post an example. Im new to this stuff.

 

[marsd]

I'm not going to write the entire script for you but I'll
post some ideas.

#function to lookup and return pid's based on program name
#usage: lookupId wget ; var=`lookupId wget`
function lookupId() { 
prog=$1       
   all=`ps -aux | grep $prog | awk ' { if ($0 !~ /grep/) {print $2}}'`     
   if [ ! -z "$all" ] ; then         
      echo $all     
   fi 
return
 }

#function to monitor and kill a running process.
#usage: sleepCheck 3600 60 wget
function sleepCheck() {
tbin=$PWD/tt
max=$1
interval=$2
prog=$3
start=`exec $tbin`
now=`exec $tbin` 
pidlist=`lookupId $prog`
     
         while :
         do
               etime=`expr $now - $start`
               if [ $etime -gt $max ] ; then
                  for all in $(echo $pidlist)
                  do
                       kill -kill $all || echo "Unable to kill $all"
                  done
                  exit 0 > /dev/null
               fi
               sleep $interval
               pidlist=`lookupId $prog`
               if [ -z "$pidlist" ] ; then 
                   echo  "No processes for $prog found"
                   exit 0 > /dev/null
               fi
               now=`exec $tbin`
         done
} 

#snippet to generate a program for epoch time
#usage: genStamp
function genStamp() {
binp=$PWD/tt
rfile=$PWD/raw.c

   if [ -e $binp ] ; then
      return 
   fi
   
     cat << EOF > $rfile
     #include <stdio.h>
     #include <time.h>  

     int main(void) {
              printf(&quot;%d\n&quot;,time(NULL));
     return 0;
     }
EOF
gcc $rfile -o $binp || echo &quot;Could not create $binp&quot;
rm $rfile
}

Functions are only basically tested.
The sleepCheck function may require some syntax
adjustments.

Hope this helps you.

 

[unix81]

Thanks a lot marsd!
That was all i needed.

 

[Duane61]

Maybe I'm missing something, but...

how about:

#!bin/sh
retreiveFtpInfo & # run FTP function in the background
retrieveFtpPid=$! # capture pid of last background process

then,

kill -9 $retrieveFtpPid # to kill the process if necessary

-or-

grep on $retrieveFtpPid and use an 'if' test to sleep until it's finished.

Duane

 

[unix81]

Thanks Duane, that was an interesting approach, and it works!