Hi, I am Indra. I am new in perl.

I start to run my script :
************************************************************ *************************************
#!/usr/bin/perl -w

$UNFOLD = 1; #1=UNFOLD^[$B%G!<%?$r;HMQ^[(B 0=^[$B [at] 8^[(Bvolume^[$B%G!<%?$r;HMQ^[(B
$XDR_NUM = 1; #1=^[$BJRJ}$N$_^[(BCAPPI^[$B$r:n [at] .^[(B 0=^[$BN>J}$N^[(BCAPPI^[$B$r:n [at] .^[(B

# work directory #
$workdir = "..";
$datadir = "../volume";
$year = "2011";

if( [at] ARGV != 1){
print "ARGV error \n";
print "firstradar velx vely \n";
exit(1);
}
.......

************************************************************ *************************************
I got this error message :
ARGV error
firstradar velx vely


please help me, how to overcame this.

regards,
Indra

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On Mar 16, 2011 11:53 AM, <indrag [at] students.itb.ac.id> wrote:
>
>
> if( [at] ARGV != 1){
>

I don't think you can look at an array like its a string like that.
Maybe string( [at] ARGV ) != 1 might work. But what you probably want is:
If( defined( $ARGV[ 0 ] ) )

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Hi Indra,

On 2011-03-16 22:51 +0700, indrag [at] students.itb.ac.id wrote:
> if( [at] ARGV !=3D 1){
> print "ARGV error \n";
> print "firstradar velx vely \n";
> exit(1);
> }

=2E..

> I got this error message :
> ARGV error
> firstradar velx vely

This is your output if the number of arguments isn't what you
expected. Guessing from

print "firstradar velx vely \n";

you probably want to change

if( [at] ARGV !=3D 1){

to

if( [at] ARGV !=3D 2){

as [at] ARGV is a list and lists in scalar context is how many elements it
contains. Makes sense?

--
- Olof Johansson
- www: http://www.stdlib.se/
- {mail,xmpp}: olof [at] ethup.se
- irc: zibri on Freenode/OFTC/IRCnet/...
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On 3/16/11 Wed Mar 16, 2011 8:51 AM, "indrag [at] students.itb.ac.id"
<indrag [at] students.itb.ac.id> scribbled:

>
> Hi, I am Indra. I am new in perl.
>
> I start to run my script :
> ************************************************************ ******************
> *******************
> #!/usr/bin/perl -w
>
> $UNFOLD = 1; #1=UNFOLD^[$B%G!<%?$r;HMQ^[(B
> 0=^[$B [at] 8^[(Bvolume^[$B%G!<%?$r;HMQ^[(B
> $XDR_NUM = 1; #1=^[$BJRJ}$N$_^[(BCAPPI^[$B$r:n [at] .^[(B
> 0=^[$BN>J}$N^[(BCAPPI^[$B$r:n [at] .^[(B
>
> # work directory #
> $workdir = "..";
> $datadir = "../volume";
> $year = "2011";
>
> if( [at] ARGV != 1){
> print "ARGV error \n";
> print "firstradar velx vely \n";
> exit(1);
> }
> ......
>
> ************************************************************ ******************
> *******************
> I got this error message :
> ARGV error
> firstradar velx vely
>
>
> please help me, how to overcame this.

Your script requires that one argument be entered on the command line, like
this:

yourscript.pl arg1

Arguments entered this way are put into the [at] ARGV array. The logical
expression ( [at] ARGV != 1) compares the number of elements in the [at] ARGV array
to 1 and returns true if they are not equal. An array in scalar context like
the above use returns the number of elements in the array.

Therefore, you should enter one argument on the command line when you
execute the script.



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On 11-03-16 12:11 PM, shawn wilson wrote:
> On Mar 16, 2011 11:53 AM,<indrag [at] students.itb.ac.id> wrote:
>>
>>
>> if( [at] ARGV != 1){
>>
>
> I don't think you can look at an array like its a string like that.
> Maybe string( [at] ARGV ) != 1 might work. But what you probably want is:
> If( defined( $ARGV[ 0 ] ) )
>

No, that is correct. In scalar context, [at] array is the number of items
in the array. The problem is that the OP is running the script without
any arguments.

On 11-03-16 11:51 AM, indrag [at] students.itb.ac.id wrote:
> if( [at] ARGV != 1){
> print "ARGV error \n";
> print "firstradar velx vely \n";
> exit(1);
> }

This code will print out an error and stop the script if there are no
arguments. Solution: run the script with arguments.


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Shawn

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On 3/16/11 Wed Mar 16, 2011 9:11 AM, "shawn wilson" <ag4ve.us [at] gmail.com>
scribbled:

> On Mar 16, 2011 11:53 AM, <indrag [at] students.itb.ac.id> wrote:
>>
>>
>> if( [at] ARGV != 1){
>>
>
> I don't think you can look at an array like its a string like that.
> Maybe string( [at] ARGV ) != 1 might work. But what you probably want is:
> If( defined( $ARGV[ 0 ] ) )

Try it!

The logical operator != gives scalar context to both left and right
operands. An array in scalar context returns the number of elements in the
array. Therefore, the expression ( [at] ARGV != 1) will return true if the number
of elements in [at] ARGV is not exactly one.



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On 2011-03-16 17:13 +0100, Olof Johansson wrote:
> This is your output if the number of arguments isn't what you
> expected. Guessing from
>
> print "firstradar velx vely \n";
>
> you probably want to change
>
> if( [at] ARGV !=3D 1){
>
> to
>
> if( [at] ARGV !=3D 2){
>
> as [at] ARGV is a list and lists in scalar context is how many elements it
> contains. Makes sense?

My brain fooled me into thinking it was a =3D=3D instead of !=3D. What you =
know
check is if [at] ARGV is not 1. I don't know why you would do this.

--
- Olof Johansson
- www: http://www.stdlib.se/
- {mail,xmpp}: olof [at] ethup.se
- irc: zibri on Freenode/OFTC/IRCnet/...
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Hi Indra,

a few comments on your code.

On Wednesday 16 Mar 2011 17:51:19 indrag [at] students.itb.ac.id wrote:
> Hi, I am Indra. I am new in perl.
>
> I start to run my script :
> ************************************************************ ***************
> **********************
>
> #!/usr/bin/perl -w
>

1. Don't use "-w".

2. Add "use strict;"

3. Add "use warnings;"

See:

http://perl-begin.org/tutorials/bad-elements/#no-strict-and- warnings

> $UNFOLD = 1; #1=UNFOLD^[$B%G!<%?$r;HMQ^[(B

1. Add my to them.

2. What are all the junk characters after the line? I cannot understand what
they mean.

> 0=^[$B [at] 8^[(Bvolume^[$B%G!<%?$r;HMQ^[(B $XDR_NUM = 1;
> #1=^[$BJRJ}$N$_^[(BCAPPI^[$B$r:n [at] .^[(B 0=^[$BN>J}$N^[(BCAPPI^[$B$r:n [at] .^[(B
>
> # work directory #
> $workdir = "..";
> $datadir = "../volume";
> $year = "2011";

1. Add my.

2. Maybe use http://perldoc.perl.org/File/Spec.html

>
> if( [at] ARGV != 1){

1. There should be a space before the "{".

> print "ARGV error \n";
> print "firstradar velx vely \n";

You should output errors STDERR - not STDOUT. Maybe use perldoc -f die
instead.

Regards,

Shlomi Fish

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Olof Johansson wrote:
>
> On 2011-03-16 22:51 +0700, indrag [at] students.itb.ac.id wrote:
>> if( [at] ARGV != 1){
>> print "ARGV error \n";
>> print "firstradar velx vely \n";
>> exit(1);
>> }
>
> ...
>
>> I got this error message :
>> ARGV error
>> firstradar velx vely
>
> This is your output if the number of arguments isn't what you
> expected. Guessing from
>
> print "firstradar velx vely \n";
>
> you probably want to change
>
> if( [at] ARGV != 1){
>
> to
>
> if( [at] ARGV != 2){
>
> as [at] ARGV is a list and lists in scalar context is how many elements it
> contains.

perldoc -q "What is the difference between a list and an array?"


[at] ARGV is an ARRAY and ARRAYs in scalar context ...



John
--
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more complex... It takes a touch of genius -
and a lot of courage to move in the opposite
direction. -- Albert Einstein

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Shlomi Fish wrote:
>
> On Wednesday 16 Mar 2011 17:51:19 indrag [at] students.itb.ac.id wrote:
>>
>> if( [at] ARGV != 1){
>
> 1. There should be a space before the "{".

There could be, but there doesn't have to be.


>> print "ARGV error \n";
>> print "firstradar velx vely \n";
>
> You should output errors STDERR - not STDOUT. Maybe use perldoc -f die
> instead.

Or perldoc -f warn



John
--
Any intelligent fool can make things bigger and
more complex... It takes a touch of genius -
and a lot of courage to move in the opposite
direction. -- Albert Einstein

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