Re: What is the source of my input, file or STDIN?
[EMAIL PROTECTED] wrote:
As I understand it, operator will open all items in @ARGV allowing
one to do a shell command line of
perl.script file1 file2 file3
and inside perl.script you only need
while () { ... syntax to read all the files on the command line.
will also open STDIN if the perl script is invoked from a pipe, such
as
ls | perl.script
So, 1. from within perl.script, how can one tell if the input stream is
coming from
STDIN or a file that was opened by ?
2. If input stream is not coming from STDIN, but a file, how can one
tell which file is the current file (assuming multiple files were
specified on the command line)?
$ARGV will contain the name of the current file or '-' if reading from
STDIN.
$ perl -le'while () {eof print $ARGV}' test.txt test1.txt
test.txt
test1.txt
$ perl -le'while () {eof print $ARGV}' test.txt
-
$ cat test.txt | perl -le'while () {eof print $ARGV}'
-
John
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Re: What is the source of my input, file or STDIN?
On Jan 6, 2004, at 1:07 PM, david wrote: [EMAIL PROTECTED] wrote: Case 3. (this is the difficult case for me) the script is invoked with no file and no pipe to it. I would like the script to end quietly, such as test.input.source Instead, it waits for input. test.input.source no command line args - switching to STDIN and now it waits forever. select / IO::Select is what you are looking for. [..] My compliments to David, as always. The reason the code is 'waiting for ever' in the case of having no STDIN is that it is in a blocking IO Read on STDIN. So since we have a better spec, I have updated the code to show how the IO::Select could be used to gate for the case that the code was called without command line input, nor a current connection for STDIN. http://www.wetware.com/drieux/pbl/perlTrick/CommandLine/ file_or_stdin.plx Note all of the noisy 'print statements' are there merely to show the transition of the logic of the code. On Jan 6, 2004, at 12:53 PM, Steve Grazzini wrote: On Jan 6, 2004, at 3:17 PM, [EMAIL PROTECTED] wrote: Case 3. (this is the difficult case for me) the script is invoked with no file and no pipe to it. I would like the script to end quietly die usage() if @ARGV == 0 and -t; You might not want to test if there is a controlling terminal - since that would prevent the pipe fitting from working unless there was a controlling terminal. A problem that will crop up when JoeBob opts wants to use the pipe fitting in their KSH script... I didn't show you how to check for the pipe (-p) because this should probably work, too: % your-script input.txt We have So got to talk about your meds here... 8-) To be honest, I had not thought about the idea of '-p' even trying to test to see if it was a pipe since it is-ish when one connects the pipe fittings of the standard shell, or as you have done, the express redirection of input... [jeeves: 30:] wc -l funk* 14 funk_env.plx [jeeves: 31:] ./file* funk* no command line args - switching to STDIN STDIN had 14 number of lines we saw 14 number of lines [jeeves: 32:] The 'redirect in' of simply is a way of changing how STDIN is feed to the calling program by the shell. It of course is dependent upon how the shell copes with re-attaching STDIN|STDOUT combo's... ciao drieux --- -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
Pipe and STDIN - Re: What is the source of my input, file or STDIN?
On Jan 6, 2004, at 12:17 PM, [EMAIL PROTECTED] wrote:
[..]
It just dawned on me that I may not be using the
correct terminology since pipe and STDIN probably
imply much more than I mean for them to convey.
[..]
This is a good angst point to raise.
Technically STDIN|STDOUT|STDERR denote
merely 'file descriptors' that will be
opened by the shell in compliance with
how the shell saw the voodoo passed to it.
Normally they will be implemented as a 'pipe'
unless we do something else with them, at
which they may be implemented as a 'closed fd'
8-)
One can implement Pipes that are not the
first three fd's in the _iobuf[] - and yes,
one can get into massed weirdness when screwing
around at that level. So the way to think about the
problem is that the first three fd's stdin|stdout|stderr
will be implemented at pipes, and as such are a proper
subset of the set of Pipes. We tend to speak in terms
of 'pipe fittings' because we think of them in terms of say
ps -ef | grep foo | egrep -v grep | awk '{print $2}'
which we on the perl side of the line could have implemented
with say perl's popen() approach of say
open(PS, ps $ps_args |) or die unable to popen(ps $ps_args): $!;
while(PS)
{
# your proc grovelling here...
}
close(PS);
But for some reason, I'd hazzard to say that about 99%
of us fail to set a $SIG{'PIPE'} handler to deal with
the prospects of the pipe breaking because, well
most of the time we just do not care. Even MORE SO
when it is stdin|stdout|stderr ...
So the converse of your kvetch is of course,
Gosh, now that I feel at home writing pipe fittings,
when, where and how would I really want to be building
my own pipes and/or popen() types of tricks?
well for that there is perldoc perlipc
for everything else, there is ioctl()
8-)
ciao
drieux
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Re: What is the source of my input, file or STDIN?
On Jan 7, 2004, at 1:10 PM, drieux wrote:
On Jan 6, 2004, at 12:53 PM, Steve Grazzini wrote:
die usage() if @ARGV == 0 and -t;
You might not want to test if there is a
controlling terminal
I want to test whether STDIN (the default argument for -t)
is hooked up to the terminal (which is what -t tells you) so
that ARGV doesn't block waiting for user input.
But if you want to quibble, this still blocks:
% perl -pe 'BEGIN{ die if @ARGV == 0 and -t }' /dev/tty
--
Steve
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-t and STDIN was Re: What is the source of my input, file or STDIN?
On Jan 7, 2004, at 10:37 AM, Steve Grazzini wrote: [..] I want to test whether STDIN (the default argument for -t) is hooked up to the terminal (which is what -t tells you) so that ARGV doesn't block waiting for user input. [..] I have absolutely no problem with the idea that one wants to use '-t' to establish that there is a controlling terminal, AKA a ttyline - but the problem is the false assumption that this is in some way associated with STDIN. IF i am going to guard my code with '-t' to establish if there is any STDIN then as soon as the code is used inside of a forked and exec'd event where the child process is no longer attached to the TTYLINE then foo | bar will break because bar, failing to find it's controlling terminal will not see the information coming at it from foo through the STDIN pipe. So if one wanted to check that there were bits in STDIN, then one should do that with the IO::Select approach - since that will tell one if there are bits on STDIN, even if the process itself is being run without a controlling terminal. To help illustrate the point: http://www.wetware.com/drieux/pbl/perlTrick/CommandLine/ got_ttyline.plx now granted, I have only tested this on darwin|freebsd|solaris|linux and only with perl 5.6 and 5.8 but they all come back with: vladimir: 67:] perl got_ttyline.plx This Will Gin Up: Mother Got Back:hello, I am /tmp/drieux/CallMe.txt Mother Got Back:what tty line? Mother Got Back:STDIN says : /tmp/drieux/SomeCmd.txt:About to shout out Mother Got Back:STDIN says : sending var1 Mother Got Back:STDIN says : sending thing2 Mother Got Back:STDIN says : sending thing3 vladimir: 68:] So it is possible that there are implementations of this which will not work in the way that I expect it - but as a general rule of thumb if one wants to know that one has a controlling terminal - -t then one should test for it. But simply because there is no controlling terminal does NOT mean that there is nothing on STDIN. So that we are clear on this, it is not merely an issue in Perl, this is even MORE depressing when it is coded in a 'realCoderLanguage[dm]' and worse YET when the dilbert made TOTALLY irrational presumptions that if there was no controlling terminal that this of course meant that the build was suppose to use some WingNarkFrimFrimFrim library that of course leads to totally wacky problems when the build by hand at a terminal works find, and all of the code builds correctly but Blows Big Ones when done in an automated environment ciao drieux --- -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
Re: -t and STDIN was Re: What is the source of my input, file or STDIN?
On Jan 7, 2004, at 2:57 PM, drieux wrote:
But simply because there is no controlling
terminal does NOT mean that there is nothing on STDIN.
Were you reading that code backwards?
die usage() if @ARGV == 0 and -t;
# if ((THERE ARE NO FILENAMES IN ARGV)
# (STDIN IS HOOKED UP TO A TERMINAL))
# {
# COMPLAIN;
# }
We only complain if STDIN *is* a tty.
I have absolutely no problem with the idea that
one wants to use '-t' to establish that there is
a controlling terminal, AKA a ttyline - but the
problem is the false assumption that this is in
some way associated with STDIN.
% perldoc -f -X
... If the argument is omitted, tests $_, except for
-t, which tests STDIN.
--
Steve
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Re: What is the source of my input, file or STDIN?
On Jan 6, 2004, at 9:32 AM, [EMAIL PROTECTED] wrote: [..] So, 1. from within perl.script, how can one tell if the input stream is coming from STDIN or a file that was opened by ? 2. If input stream is not coming from STDIN, but a file, how can one tell which file is the current file (assuming multiple files were specified on the command line)? This is gonna sound a bit silly, so laugh along with me while I play this out. If you want to know which is the whom For What, why not simply code it that way? As an illustration: http://www.wetware.com/drieux/pbl/perlTrick/CommandLine/ file_or_stdin.plx In this case I will walk the @ARGV if there is anything to walk, test that the file exists, then pass it off to a count_lines() function, which will open it and count the number of lines. If there are no arguments at the command line, then we will call count_lines() without a file name. On the inside of the count_lines() function is the trick $file ||= '-'; # we open STDIN unless file either we were passed a file name to open, or we will set $file to '-' so that it will read from STDIN. cf: perldoc -f open ciao drieux --- -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
Re: What is the source of my input, file or STDIN?
From: [EMAIL PROTECTED]
As I understand it, operator will open all items in @ARGV allowing
one to do a shell command line of
perl.script file1 file2 file3
and inside perl.script you only need
while () { ... syntax to read all the files on the command line.
will also open STDIN if the perl script is invoked from a pipe,
such as
ls | perl.script
So, 1. from within perl.script, how can one tell if the input stream
is coming from STDIN or a file that was opened by ?
2. If input stream is not coming from STDIN, but a file, how can one
tell which file is the current file (assuming multiple files were
specified on the command line)?
From perldoc perlvar:
$ARGV contains the name of the current file when reading from
.
HTH, Jenda
= [EMAIL PROTECTED] === http://Jenda.Krynicky.cz =
When it comes to wine, women and song, wizards are allowed
to get drunk and croon as much as they like.
-- Terry Pratchett in Sourcery
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Re: What is the source of my input, file or STDIN?
So, 1. from within perl.script, how can one tell if the input stream is coming from STDIN or a file that was opened by ? Use select 2. If input stream is not coming from STDIN, but a file, how can one tell which file is the current file (assuming multiple files were specified on the command line)? My solution is the hard way. Open the files yourself and use the respective filenames as their filehandles. That is: open($foo, $foo) or die Could not open $foo: $!\n; __ William Ampeh (x3939) Federal Reserve Board -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
RE: What is the source of my input, file or STDIN?
Thanks for the help drieux. I could have been more explicit in my question to have stated that I want perl.script to exit quietly if there are no files on the command line or if not invoked as the recipient of piped output. I tested your code (I named the file test.input.source) and ... Case 1. a file is specified - works as desired. test.input.source test.input.source file test.input.source had 59 number of lines we saw 59 number of lines Case 2. a file is cat'd to test.input.source - works as desired. cat test.input.source |test.input.source no command line args - switching to STDIN STDIN had 59 number of lines we saw 59 number of lines Case 3. (this is the difficult case for me) the script is invoked with no file and no pipe to it. I would like the script to end quietly, such as test.input.source Instead, it waits for input. test.input.source no command line args - switching to STDIN and now it waits forever. So I do not want to explicitly open STDIN if there is not a pipe already waiting to send me data. It just dawned on me that I may not be using the correct terminology since pipe and STDIN probably imply much more than I mean for them to convey. I hope this is more clear. And again, thanks for your help. - Paul -Original Message- From: drieux [mailto:[EMAIL PROTECTED] Sent: Tuesday, January 06, 2004 11:20 AM To: Perl Beginners Mailing List Subject: Re: What is the source of my input, file or STDIN? On Jan 6, 2004, at 9:32 AM, [EMAIL PROTECTED] wrote: [..] So, 1. from within perl.script, how can one tell if the input stream is coming from STDIN or a file that was opened by ? 2. If input stream is not coming from STDIN, but a file, how can one tell which file is the current file (assuming multiple files were specified on the command line)? This is gonna sound a bit silly, so laugh along with me while I play this out. If you want to know which is the whom For What, why not simply code it that way? As an illustration: http://www.wetware.com/drieux/pbl/perlTrick/CommandLine/ file_or_stdin.plx In this case I will walk the @ARGV if there is anything to walk, test that the file exists, then pass it off to a count_lines() function, which will open it and count the number of lines. If there are no arguments at the command line, then we will call count_lines() without a file name. On the inside of the count_lines() function is the trick $file ||= '-'; # we open STDIN unless file either we were passed a file name to open, or we will set $file to '-' so that it will read from STDIN. cf: perldoc -f open ciao drieux --- -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
RE: What is the source of my input, file or STDIN?
[EMAIL PROTECTED] wrote:
Case 3. (this is the difficult case for me) the script is invoked
with no file and no pipe to it. I would like the script to
end quietly, such as
test.input.source
Instead, it waits for input.
test.input.source
no command line args - switching to STDIN
and now it waits forever.
select / IO::Select is what you are looking for. i suggested the following
to someone who asked exactly the same question a while back. if you have
searched this group hard enough, you would have found the solution:
#!/usr/bin/perl -w
use strict;
#--
#-- script.pl
#--
use IO::Select;
if(@ARGV){
print join(\n, get file: ,@ARGV) . \n;
}else{
my $buf;
my $line;
my $io = IO::Select-new(\*STDIN);
while($io-can_read(0)){
last unless(sysread(STDIN,$buf,1024));
$line .= $buf;
}
if(defined $line){
print get line $line;
}else{
print STDERR no input\n;
}
}
__END__
[panda]$ script.pl
no input
[panda]$ script.pl file.html
get file:
file.html
[panda]$ echo hi | script.pl
get line hi
[panda]$
perldoc -f select
perldoc IO::Select
david
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sub'__{print@_ ;* \ = * ___ ,\ \}
sub'___{print@_ ;* \ = * ,\ \}
sub'{print@_,\n}{_+Just}(another)-(Perl)-(Hacker)
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Re: What is the source of my input, file or STDIN?
On Jan 6, 2004, at 3:17 PM, [EMAIL PROTECTED] wrote: Case 3. (this is the difficult case for me) the script is invoked with no file and no pipe to it. I would like the script to end quietly die usage() if @ARGV == 0 and -t; I didn't show you how to check for the pipe (-p) because this should probably work, too: % your-script input.txt -- Steve -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
Re: What is the source of my input, file or STDIN?
[EMAIL PROTECTED] wrote: So, 1. from within perl.script, how can one tell if the input stream is coming from STDIN or a file that was opened by ? Use select 2. If input stream is not coming from STDIN, but a file, how can one tell which file is the current file (assuming multiple files were specified on the command line)? My solution is the hard way. Open the files yourself and use the respective filenames as their filehandles. That is: open($foo, $foo) or die Could not open $foo: $!\n; __ William Ampeh (x3939) Federal Reserve Board I'd go with your solution. The mass-file operator surely has its place, but I think it gets over-emphasized.Right offhand, I have hard time imagining a context in which I would want to do homogeous processing with a whole argument list of files. In the cases where I would want to, I can't imagine wanting to type them in at a command-line. I can't help but suspect that this gets used way too much as a symptom of operator fetishism. Joseph -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
Re: What is the source of my input, file or STDIN?
[EMAIL PROTECTED] wrote: Thanks for the help drieux. I could have been more explicit in my question to have stated that I want perl.script to exit quietly if there are no files on the command line or if not invoked as the recipient of piped output. So what have you tried to adjust the code for this desired effect? Joseph -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] http://learn.perl.org/ http://learn.perl.org/first-response
