exec() incomplete $output

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  • ajh
    #1

    exec() incomplete $output

    Using Ubuntu 5, Apache2 and PHP 4 I am trying display in a web browser
    the output from a program I wrote in C.

    Here is an abridged version of my code (I can post all of it later):

    <?php

    exec( "myProg -a paramA -b paramB", $output);

    print "<p>Returne d: $return</p>";

    foreach ( $output as $val ) {
    print "$val<br />";
    }

    ?>

    The problem is that in the web browser only the first two lines of the
    $output appear when there should almost always more than that (usually
    around 10).

    I have done a test with php CLI using the same code as above: php -f
    mycode. The right/expected ouput comes out here.

    Any ideas how this different behaviour might be happening? Wondering if
    there is some default limit on the number of lines displayed by php in
    the browser... or if the actual lines are too long (but 100 chars isn't
    too much is it?). Thanks.

    Tags: None
    • Erwin Moller
      #2
      Re: exec() incomplete $output

      ajh wrote:
      Using Ubuntu 5, Apache2 and PHP 4 I am trying display in a web browser
      the output from a program I wrote in C.
      >
      Here is an abridged version of my code (I can post all of it later):
      >
      <?php
      >
      exec( "myProg -a paramA -b paramB", $output);
      >
      print "<p>Returne d: $return</p>";
      You forgot $return in your above call. I expect you did strip your example
      here. If not you would probably have received a notice about it.
      (You DO have error_reporting on to the max, right? Check php.ini or make
      sure you see all errors by calling ini_set() above your script.)
      >
      foreach ( $output as $val ) {
      print "$val<br />";
      }
      That should work.
      It prints literally to the browser what the program returned.
      However, this output could contain things like < starting a html-tag.

      So if you actually want to see the output generated in a browser, try this:

      foreach ( $output as $val ) {
      echo htmlentities($v al)."<br>";
      }

      If this wasn't the case, make sure you have error_reporting on, if that
      doesn't help (= no errors/notices) come back here and please post more
      code.

      Regards,
      Erwin Moller
      >
      ?>
      >
      The problem is that in the web browser only the first two lines of the
      $output appear when there should almost always more than that (usually
      around 10).
      >
      I have done a test with php CLI using the same code as above: php -f
      mycode. The right/expected ouput comes out here.
      >
      Any ideas how this different behaviour might be happening? Wondering if
      there is some default limit on the number of lines displayed by php in
      the browser... or if the actual lines are too long (but 100 chars isn't
      too much is it?). Thanks.

        Comment

        • ajh
          #3
          Re: exec() incomplete $output

          Thanks for your suggestions Erwin. I've turned on all the error
          messages and done some minor debugging. Nothing that related to the
          output though. The underlying program is a basic search engine - you
          are right about the html output so I made that htmlentities change but
          it didn't make a difference.

          Here is the code:


          <?php

          define("PROG", "/blah/bling/query");

          $crawl = "courses";

          $indexfile = "$crawl.csv ";
          $crawldir = "$crawl";
          $namesfile = "$crawl.nam es";
          $rankfile = "$crawl.ran k";
          $maxhits = 10;
          $querystr = escapeshellarg( $_GET['query']);

          // Check if querystr is present
          if ($querystr!=NUL L)
          {
          // Run the query
          unset($out);
          exec("echo " . $querystr . " | " . PROG . " -i $indexfile -d
          $crawldir -n $namesfile -p $rankfile -m $maxhits", $out);
          }

          ?>

          <html>
          <body bgcolor="#fffff f">

          <br>
          <br>
          <form method="get" action="<?php print $_SERVER['PHP_SELF']?>">
          <input name="query" type="text" size="50" maxlength="50">
          <input type="button" value="submit" />
          </form>

          <br>
          <br>

          <?php
          // show output
          foreach ($out as $val)
          {
          echo htmlentities($v al)."<br/>";
          }
          ?>

          </body>
          </html>

            Comment

            • Erwin Moller
              #4
              Re: exec() incomplete $output

              ajh wrote:
              Thanks for your suggestions Erwin. I've turned on all the error
              messages and done some minor debugging. Nothing that related to the
              output though. The underlying program is a basic search engine - you
              are right about the html output so I made that htmlentities change but
              it didn't make a difference.
              >
              Here is the code:
              >
              >
              <?php
              >
              define("PROG", "/blah/bling/query");
              >
              $crawl = "courses";
              >
              $indexfile = "$crawl.csv ";
              $crawldir = "$crawl";
              $namesfile = "$crawl.nam es";
              $rankfile = "$crawl.ran k";
              $maxhits = 10;
              $querystr = escapeshellarg( $_GET['query']);
              >
              // Check if querystr is present
              if ($querystr!=NUL L)
              {
              // Run the query
              unset($out);
              exec("echo " . $querystr . " | " . PROG . " -i $indexfile -d
              $crawldir -n $namesfile -p $rankfile -m $maxhits", $out);
              }
              >
              ?>
              >
              <html>
              <body bgcolor="#fffff f">
              >
              <br>
              <br>
              <form method="get" action="<?php print $_SERVER['PHP_SELF']?>">
              <input name="query" type="text" size="50" maxlength="50">
              <input type="button" value="submit" />
              </form>
              >
              <br>
              <br>
              >
              <?php
              // show output
              foreach ($out as $val)
              {
              echo htmlentities($v al)."<br/>";
              }
              ?>
              >
              </body>
              </html>
              Hi,

              Well, that is strange indeed.
              As far as I can see your approach works, and I do not see any reason why a
              call to the program works from a shell, but not via PHP.

              2 things you can try:
              1) Environment:
              Before executing the command, create it in a string and echo that.
              Copy/paste it into a shell, WITH the same environment as your PHP script,
              and see if that works as expected. (use phpinfo() to find settings of
              interest)
              Some missing environmentvari able could maybe screw up the execution of your
              program?

              2) Catch the result again as you did halfheartedly ;-) in your first
              posting.
              Do add the $result again as third argument to the exec(), and see if that
              contains anything of interest after you called exec.
              It could possibly contain some error.

              Regards,
              Erwin Moller

                Comment

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