I need to detect if input has been to my script or not.

For example, I would like to differentiate between an invocation from
the two lists below:

Examples where input is "provided":
perl myscript.pl input.txt
perl myscript.pl < input.txt
executable_that_writes_to_sdtout | perl myscript.pl

Example of where no input is "provided":
perl myscript.pl

---

I've tried:

if (seek(STDIN,0,1)) {
#input provided
}
else {
# no input provided
}

which appears to work if an input file was specified or redirection
was done but does not work for piped data.

If (eof(STDIN)) {
}

which blocks if no input was provided.

I'm using Windows XP.


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On 3/14/11 Mon Mar 14, 2011 1:49 PM, "Mark" <google [at] markginsburg.com>
scribbled:

> I need to detect if input has been to my script or not.
>
> For example, I would like to differentiate between an invocation from
> the two lists below:
>
> Examples where input is "provided":
> perl myscript.pl input.txt
> perl myscript.pl < input.txt
> executable_that_writes_to_sdtout | perl myscript.pl
>
> Example of where no input is "provided":
> perl myscript.pl
>

> I'm using Windows XP.
>

The standard Unix function for determining this is isatty(in fd), where fd
is the file descriptor for the input/output stream. I don't know the
equivalent in Windows. However, there is the file test operator -t that
returns true if "Filehandle is opened to a tty", and the POSIX module
includes the isatty function. Try those.

perldoc -f -X
perldoc POSIX



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On 11-03-14 04:49 PM, Mark wrote:
> Examples where input is "provided":
> perl myscript.pl input.txt
> perl myscript.pl< input.txt
> executable_that_writes_to_sdtout | perl myscript.pl
>
> Example of where no input is "provided":
> perl myscript.pl
>

my $has_input = 0;
while( <> ){
$has_input = 1;
# process the input line by line
}
if( ! $has_input ){
# do something else
}


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On Mar 14, 2:06=A0pm, jimsgib... [at] gmail.com (Jim Gibson) wrote:
> The standard Unix function for determining this is isatty(in fd), where f=
d
> is the file descriptor for the input/output stream. I don't know the
> equivalent in Windows. However, there is the file test operator -t that
> returns true if "Filehandle is opened to a tty", and the POSIX module
> includes the isatty function. Try those.

Yes! The -t test did the trick.

Thanks Jim.


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