Checking for STDIN

dbmathis has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: Checking for STDIN by AltBlue (Chaplain) on Jul 30, 2008 at 01:31 UTC
-t `STDIN`	[reply] [d/l]
Re^2: Checking for STDIN by Anonymous Monk on Jul 30, 2008 at 01:35 UTC
-t will not work because I am using my script in a cron job sometimes.	[reply]
Re^3: Checking for STDIN by AltBlue (Chaplain) on Jul 30, 2008 at 02:03 UTC
What do you mean?! Save this code to a file and test it. `#!/usr/bin/perl -wl use strict; open my $fh, '>', '/tmp/test.log' or die $!; print $fh 'STDIN ', ( -t STDIN ? 'IS' : 'is NOT' ), ' available' or di +e $!; close $fh or die $!;` [download]	[reply] [d/l]
Re^4: Checking for STDIN by dbmathis (Scribe) on Jul 30, 2008 at 02:09 UTC
Re^5: Checking for STDIN by AltBlue (Chaplain) on Jul 30, 2008 at 02:16 UTC
Some notes below your chosen depth have not been shown here
Re: Checking for STDIN by jethro (Monsignor) on Jul 30, 2008 at 01:53 UTC
STDIN is for reading, a logfile usually for writing. Do you really want to read from the logfile ? Also, please put some dividing line between your text and your sig. I don't know if I'm the only one, but having to read your sig everytime because I get the impression it is part of the text is somewhat like getting spam.	[reply]
Re^2: Checking for STDIN by dbmathis (Scribe) on Jul 30, 2008 at 02:05 UTC
I have a perl script that at the moment has a command line option -logfile <file> where it gets input by reading the <file> into the script. I would like to be able to check to see if stdin is being piped into my file so that I can change the flow of my script and get my input for the pipe instead. When the -t option is used within a cron job the -t test evalutes to false or in my case it would make my script appear to be having input piped to it when in fact in my cron job I have -logfile <file> specified. Make sense?	[reply]
Re^3: Checking for STDIN by ikegami (Patriarch) on Jul 30, 2008 at 02:22 UTC
Sounds like what you actually want to do is check of -logfile was specified.	[reply]
Re^4: Checking for STDIN by dbmathis (Scribe) on Jul 30, 2008 at 02:38 UTC
Re^5: Checking for STDIN by ikegami (Patriarch) on Jul 30, 2008 at 09:14 UTC
Some notes below your chosen depth have not been shown here
Re: Checking for STDIN by Bloodnok (Vicar) on Jul 30, 2008 at 10:43 UTC
Shell scripts tend to use the `$-` environment variable in order to distinguish between interactive and non-interactive e.g. cron, invocations - it being set for interactive invocations. HTH, Update Note, also, that if invoked non-interactively e.g. by cron(1), the environment is very basic i.e. none of the login scripts will have been run, so it's always best to invoke them in the cron(1) command e.g. `* * * * * . $HOME/profile ; some_cmd > /dev/null 2>&1` At last, a user level that overstates my experience :-))	[reply] [d/l] [select]