run a bash script with many argument

Question

I have a system with over 20 network devices backing up running config to a backup server. On the server side I have to check if the backup jobs are still working. So I have this script:

SHELL=/bin/bash
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

device="$1"
backupdir="/backup/$device"
latestbackup="`find $backupdir -mmin -1440 -name "$device*"`"
if [[ -f $latestbackup ]];
 then
  echo "`date` - $device - latest backup is $latestbackup"
 else
  echo "`date` - $device - backup not working"
fi

so I can run this script with following statement:

./backup.sh router1

Is there anyway to make this script available with many more arguments? (over 20) like:

./backup.sh router1 router2 router3 ...

Nir Alfasi · Accepted Answer · 2015-10-09 02:45:47Z

2

You can run the script in a loop, each time with another argument:

for x in router1 router2 router3 ...; do ./backup.sh $x; done;

answered Oct 9, 2015 at 2:45

Nir Alfasi

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4 Comments

mklement0 Over a year ago

A pragmatic alternative to having to modify the script.

Nir Alfasi Over a year ago

@mklement0 if it's something that will be used like this more than once I'd change the script, but for "one off" I would hack it with the one-liner above ;)

mklement0 Over a year ago

Fully agreed; that's exactly the sentiment I was trying to express in my comment; unfortunately, someone voted your answer down.

Nir Alfasi Over a year ago

@mklement0 I see lots of trolls here lately (I consider anyone who downvotes and does not comment to explain why as a troll).

Andy Guibert · Accepted Answer · 2015-10-09 12:36:39Z

0

You can use the $@ special parameter here -- which represents the entire argument string (1st argument and later) in conjunction with a for loop.

The code would look like this:

SHELL=/bin/bash
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

for device in "$@"; do
  backupdir="/backup/$device"
  latestbackup="`find $backupdir -mmin -1440 -name "$device*"`"
  if [[ -f $latestbackup ]];
    then
    echo "`date` - $device - latest backup is $latestbackup"
  else
    echo "`date` - $device - backup not working"
  fi
done

edited Oct 9, 2015 at 12:36

answered Oct 9, 2015 at 2:49

Andy Guibert

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4 Comments

mklement0 Over a year ago

While $@ will probably work in this particular case, it is generally advisable to use "$@" - note the enclosing double-quotes - for robustness, as only that ensures that the original partitioning of the command line into arguments is preserved. Terminology quibble: $@ is a special parameter in Bash parlance, not an operator.

Andy Guibert Over a year ago

Thanks @mklement0, updated my answer. Didn't know that "$@" was preferred, as it still worked when I tested it out initially, but your explanation makes sense.

mklement0 Over a year ago

@aguibert: Thanks for updating your answer; to give a concrete example as to why unquoted $@ is problematic: bash -c 'for a in $@; do echo "[$a]"; done' '(unused)' 'nospaces' 'with spaces' '*' - as you'll see, word splitting and pathname expansions (globbing) are applied, so that the 2nd argument is split into 2, and the 3rd argument is pathname-expanded.

mklement0 Over a year ago

@aguibert: Another handy, though somewhat obscure option is to simply use for device; do ... (sic) - this is equivalent to for device in "$@"; do ...

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