From bug-octave-request at bevo dot che dot wisc dot edu  Wed Jan 26 16:22:16 2000
Subject: popen2 broken? 
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: bsapp at lanl dot gov
Cc: bug-octave at bevo dot che dot wisc dot edu
Date: Wed, 26 Jan 2000 16:22:36 -0600 (CST)

On 26-Jan-2000, Ben Sapp <bsapp at nua dot lampf dot lanl dot gov> wrote:

| In octave-2.1.23 on Linux and octave-2.1.24 on IRIX the example given in
| the documentation for popen2 fails.  It creates a new octave process. 
| These processes fight for stdin.  Here is the output:
| 
| -----------------------------------------------------------------
| octave:6> OCTAVE_VERSION
| OCTAVE_VERSION = 2.1.23
| octave:7> [in, out, pid] = popen2("sort","-nr")
| error: octave_base_value::double_value (): wrong type argument `list'
| error: octave_base_value::double_value (): wrong type argument `list'
| error: file id must be a file object, string, or integer value
| error: evaluating if command near line 72, column 2
| error: evaluating if command near line 68, column 7
| error: evaluating if command near line 63, column 5
| error: evaluating if command near line 57, column 3
| error: called from `popen2' in file
| `/usr/local/share/octave/2.1.23/m/miscellaneous/popen2.m'
| octave:7> error: file id must be a file object, string, or integer value
| error: evaluating if command near line 72, column 2
| error: evaluating if command near line 68, column 7
| error: evaluating if command near line 63, column 5
| error: evaluating if command near line 57, column 3
| error: called from `popen2' in file
| `/usr/local/share/octave/2.1.23/m/miscellaneous/popen2.m'
| octave:7> 
| -------------------------------------------------------------------

Here is a solution for the `wrong type' errors:

Index: popen2.m
===================================================================
RCS file: /usr/local/cvsroot/octave/scripts/miscellaneous/popen2.m,v
retrieving revision 1.12
diff -u -r1.12 popen2.m
--- popen2.m	2000/01/13 08:40:15	1.12
+++ popen2.m	2000/01/26 22:20:34
 at @ -71,14 +71,14 @@
 
         if (pid == 0)
 
-          fclose (stdin_pipe (2));
-          fclose (stdout_pipe (1));
+          fclose (nth (stdin_pipe, 2));
+          fclose (nth (stdout_pipe, 1));
 
-          dup2 (stdin_pipe (1), stdin);
-          fclose (stdin_pipe (1));
+          dup2 (nth (stdin_pipe, 1), stdin);
+          fclose (nth (stdin_pipe, 1));
 
-          dup2 (stdout_pipe (2), stdout);
-          fclose (stdout_pipe (2));
+          dup2 (nth (stdout_pipe, 2), stdout);
+          fclose (nth (stdout_pipe, 2));
 
           if (exec (command, args) < 0)
             error ("popen2: unable to start process `%s'", command);
 at @ -87,14 +87,14 @@
 
         elseif (pid)
 
-          fclose (stdin_pipe (1));
-          fclose (stdout_pipe (2));
+          fclose (nth (stdin_pipe, 1));
+          fclose (nth (stdout_pipe, 2));
 
-          if (fcntl (stdout_pipe (1), __F_SETFL__, __O_NONBLOCK__) < 0)
+          if (fcntl (nth (stdout_pipe, 1), __F_SETFL__, __O_NONBLOCK__) < 0)
             error ("popen2: error setting file mode");
           else
-            in = stdin_pipe (2);
-            out = stdout_pipe (1);
+            in = nth (stdin_pipe, 2);
+            out = nth (stdout_pipe, 1);
           endif
 
         elseif (pid < 0)


Unfortunately, I'm still having problems with reading from the output
end of the process.  It seems to hang, and I don't know why.  If
anyone can offer clues, I'd appreciate it...

jwe



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