Re: [Help-bash] View Positional Parameters of Commands

[Clark Wang]

On Wed, Jul 29, 2015 at 9:10 AM, Michael Convey <address@hidden> wrote:

> ​​
> On Tue, Jul 28, 2015 at 8:12 AM, Clark Wang <address@hidden> wrote:
>
>> For example:
>>
>
>>   $ foo() { echo $0 $1 $2; }
>>   $ foo
>>   /Users/clarkw/utils/bin/bash
>>   $ foo -a
>>   /Users/clarkw/utils/bin/bash -a
>>   $ foo -al
>>
>> ​​
>> /Users/clarkw/utils/bin/bash -al
>>   $ foo -al bar
>>
>> ​​
>> /Users/clarkw/utils/bin/bash -al bar
>>   $
>>
>
> ​​Excellent example thank you. I'm still unclear why the output of your
> last command is,
>
> ​
> ​
> ​
>  /Users/clarkw/utils/bin/bash -al bar
> ​
> ​instead of,
>
> foo ​-al bar
> ?
>

$0 expands to the name of the shell or shell script. To get the current
function name in a function, use $FUNCNAME. E.g.:

  $ foo() { echo $FUNCNAME; }
  $ foo
  foo
  $

Note that FUNCNAME becomes an array starting from bash 3.0 but the above
code still works because $array is the same as ${array[0]}.

> ​
> ​
>
> On Tue, Jul 28, 2015 at 11:12 PM, Clark Wang <address@hidden> wrote:​
>
> Or you can change current shell's $*N* like this:
>
>
This is not accurate. Functions can have their own positional parameters.

>
>   # echo "<$0> <$1> <$2>"
>   </Users/clarkw/utils/bin/bash> <> <>
>   # set -- -a
>   # echo "<$0> <$1> <$2>"
>   </Users/clarkw/utils/bin/bash> <-a> <>
>   # set -- -al
>   # echo "<$0> <$1> <$2>"
>   </Users/clarkw/utils/bin/bash> <-al> <>
>   # set -- -al bar
>   #
> ​​
> echo "<$0> <$1> <$2>"
>   </Users/clarkw/utils/bin/bash> <-al> <bar>
>   #
>
>
> Fascinating! Why doesn't this work?
>
> ​$ foo() { echo $0 $1 $2 $3 $4; }
> $ foo -a -b -c
> bash -a -b -c
> $
> ​
> echo "<$0> <$1> <$2>"
> bash <> <>
>
> Is it because 'foo()' is run in a subshell and 'echo "<$0> <$1> <$2>"' is
> run in the parent shell? If so, then the set command is not run in a
> subshell, right?
>

It's not run in a subshell. Functions have their own $*N* vars can they
would not affect the current shell's $*N* (just like *local* vars in
functions).

-clark