23

I'm trying to create a function method in a bash script that executes a command which is supplied to the method by the paramters.

Meaning somethings like this:

special_execute()
{
    # Some code

    # Here's the point where the command gets executed
    $@

    # More code
}

special_execute echo "abc"

I already tried I $@, "$@", $*, "$*" how could I do that?

8
  • $@ works for me.. special() { $@; } ... special echo "foo" gives foo
    – Drav Sloan
    Aug 28, 2013 at 0:54
  • It did not work for me with: perl -MTime::HiRes=sleep -le 'for(1..100) { print; sleep 0.05; }' and tar -cvf "backups/test.tar" -P "backups/uncompressed_server_backup_(DO NOT TOUCH!)/server/"
    – BrainStone
    Aug 28, 2013 at 0:55
  • 3
    use quotes around "$@", then you will have more success :)
    – Drav Sloan
    Aug 28, 2013 at 0:59
  • Ok. Now it works. it seems like I messed up the code arround the actual call.
    – BrainStone
    Aug 28, 2013 at 1:04
  • 1
    no problem, we all have those moments :)
    – Drav Sloan
    Aug 28, 2013 at 1:06

1 Answer 1

17

I think it's just a quoting issue when you're passing the arguments into the function.

Try calling it like so:

$ special_execute "echo 'abc'"
'abc'

If you don't want the single quotes around abc then change the quoting like this:

$ special_execute "echo abc"
abc

Debugging

You can wrap the internals of the function so that it echoes out with more verbosity.

$ function special_execute() { set -x; "$@"; set +x; }

Then when you run commands through the function, special_execute you can see what's going on.

ps example:

$ special_execute ps -eaf
+ ps -eaf
UID        PID  PPID  C STIME TTY          TIME CMD
root         1     0  0 Aug21 ?        00:00:01 /sbin/init
root         2     0  0 Aug21 ?        00:00:00 [kthreadd]
...

perl example:

$ special_execute perl -MTime::HiRes=sleep -le 'for(1..10) { print; sleep 0.05; }'
+ perl -MTime::HiRes=sleep -le 'for(1..10) { print; sleep 0.05; }'
1
2
3
4
5
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8
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10
+ set +x

Parsing argument $1

You could do something like this to parse any arguments passed in as $1.

$ function special_execute() { 
    [ "$1" -eq "-123" ] && echo "flagY" || echo "flagN"; 
    shift; 
    set -x; "$@"; set +x; 
  }

Example

with debugging enabled:

$ special_execute -123 perl -MTime::HiRes=sleep -le 'for(1..5) { print; sleep 0.05; }'
flagY
+ perl -MTime::HiRes=sleep -le 'for(1..5) { print; sleep 0.05; }'
1
2
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+ set +x

with debugging off - -123:

$ special_execute -123 perl -MTime::HiRes=sleep -le 'for(1..5) { print; sleep 0.05; }'
flagY
1
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5

with debugging off - -456:

$ special_execute -456 perl -MTime::HiRes=sleep -le 'for(1..5) { print; sleep 0.05; }'
flagN
1
2
3
4
5
2
  • Why do I get an error saying 'command not found' when using aliases?
    – Elie G.
    Aug 14, 2019 at 15:49
  • @DrunkenPoney - no such cmd, it's alias.
    – slm
    Aug 14, 2019 at 18:49

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