Bash array with loop

Question

I wrote a Bash script which tries to find a process and run the process if it had stopped. This is the script.

#!/bin/bash
process=thin
path=/home/deepak/abc/
initiate=thin start -d

process_id=`ps -ef | pgrep $process | wc -m`

if [ "$process_id" -gt "0" ]; then
  echo "The process process is running!!"
else     
  cd $path    
  $initiate
  echo "Oops the process has stopped"    
fi

This worked fine and I thought of using arrays so that i can form a loop use this script to check multiple processes. So I modified my script like this

#!/bin/bash
process[1]=thin
path[1]=/home/deepak/abc/
initiate[1]=thin start -d

process_id=`ps -ef | pgrep $process[1] | wc -m`

if [ "$process_id" -gt "0" ]; then
  echo "Hurray the process ${process[1]} is running!!"
else
  cd ${path[1]}
  ${initiate[1]}
  echo "Oops the process has stopped"
  echo "Continue your coffee, the process has been stated again! ;)"
fi

I get this error if i run this script.

DontWorry.sh: 2: process[1]=thin: not found
DontWorry.sh: 3: path[1]=/home/deepak/abc/: not found
DontWorry.sh: 4: initiate[1]=thin start -d: not found 

I googled to find any solution for this, most them insisted to use "#!/bin/bash" instead of "#!/bin/sh". I tried both but nothing worked. What am i missing?

Answer 1

I was not actually aware you could set arrays like that. I've always used:

pax> initiate=("thin start -d" "xx")
pax> echo ${initiate[0]}
thin start -d
pax> echo ${initiate[1]}
xx

You may need quotes around the strings. In my bash (4.0.33),

initiate[1]=thin start -d

is being interpreted as "set initiate[1]=thin then run start -d" because you can:

fspec=/etc/passwd ls -al ${fspec}

to set an environment variable for a single command. What version of bash are you running (use bash --version)?

Update:

Deepak, I've gotten that script working under the same release of bash as yours. See the following transcript:

pax> bash --version
GNU bash, version 3.2.48(21)-release (i686-pc-cygwin)
Copyright (C) 2007 Free Software Foundation, Inc.

pax> cat qq.sh
#!/bin/bash
process=(sleep)
path=(/)
initiate=("sleep 3600")

process_id=`ps -ef | pgrep ${process[0]} | wc -m`

if [ "$process_id" -gt "0" ]; then
    echo "Hurray the process ${process[0]} is running!!"
else
    cd ${path[0]}
    ${initiate[0]} &
    echo "Oops the process has stopped"
    echo "Continue your coffee, the process has been stated again! ;)"
fi

pax> ./qq.sh
Oops the process has stopped
Continue your coffee, the process has been stated again! ;)

pax> ./qq.sh
Hurray the process sleep is running!!

pax> ps -ef
UID     PID    PPID TTY     STIME COMMAND
pax     112       1 con  10:16:24 /usr/bin/bash
pax    4568       1 con  10:23:07 /usr/bin/sleep
pax    5924     112 con  10:23:18 /usr/bin/ps

Can you try the modified script in your own environment and see how it goes?

Answer 2

Deepak Prasanna, you may want to rethink the way you are monitoring the process.

lhunath gives reasons for not using ps to monitor/restart processes, and also a simple script wrapper to achieve the goal in a cleaner manner.

Answer 3

Perhaps something like this:

#!/usr/bin/perl -w
use strict;

my @processes = ({process=>'thin',
                  path=>'/home/deepak/abc/',
                  initiate=>'thin start -d'
                 },
                 # more records go here...
                );

for $p (@processes) {
   my $cmd = 'ps -ef | pgrep ' . $p->{process} . ' | wc -m';
   if (`$cmd` > 0) {
     print "The process process is running!!\n";
   } else {
     exec('cd ' . $p->{path} . '; ' .  
          $p->{$initiate}. '; '.
          'echo Oops the process has stopped'); 
   }
}