[Octave-bug-tracker] [bug #49864] fscanf incomplete read with popen

[Denis Sbragion]

URL:
  <http://savannah.gnu.org/bugs/?49864>

                 Summary: fscanf incomplete read with popen
                 Project: GNU Octave
            Submitted by: dsbragion
            Submitted on: Fri 16 Dec 2016 02:37:27 PM GMT
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: fscanf, popen
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.2.0
        Operating System: Microsoft Windows

    _______________________________________________________

Details:

Hello,

the attacched script and test file could be used to reproduce the bug. The
script simply performs the same file read both through a standard file and a
popen pipe:


pp = fopen('testfile.txt','rt');
size(fscanf(pp,'%f;%f'))
fclose(pp);

pp = popen('type testfile.txt','r');
size(fscanf(pp,'%f;%f'))
pclose(pp);


The two sections of the script of course should provide the same output.
"testfile.txt" is just a sequence of comma separated numbers, nothing
special.

With Octave 4.0.3 the result is correct:


octave:7> fscanfbug
ans =

   3240      1

ans =

   3240      1


With Octave 4.2.0 I get the following output:


octave:4> fscanfbug
Il processo ha tentato di scrivere in una pipe non esistente.
ans =

   3240      1

ans =

   4   1


The error message at the top translated means "The process tried to write to a
non existant pipe".

It looks like fscanf stops reading before the "type" command finishes to write
its output, so the following pclose closes the pipe and then the error. 

Thanks in advance for your attention.

Bye,

Denis Sbragion



    _______________________________________________________

File Attachments:


-------------------------------------------------------
Date: Fri 16 Dec 2016 02:37:27 PM GMT  Name: fscanfbug.m  Size: 144B   By:
dsbragion
Test script and sample input file
<http://savannah.gnu.org/bugs/download.php?file_id=39251>
-------------------------------------------------------
Date: Fri 16 Dec 2016 02:37:27 PM GMT  Name: testfile.txt  Size: 17kB   By:
dsbragion
Test script and sample input file
<http://savannah.gnu.org/bugs/download.php?file_id=39252>

    _______________________________________________________

Reply to this item at:

  <http://savannah.gnu.org/bugs/?49864>

_______________________________________________
  Message sent via/by Savannah
  http://savannah.gnu.org/