I'm struggling with trying to identify a failure in a set of piped commands run on a remote host via ssh. I use perl to build and run the command line as below 
ssh $TARGET_HOST "sudo find $TARGET_DIR -name \'$TARGET_FILE\' | sudo 
+cpio --create --format ustar" | bzip2 -9 -c

[download]
Initially I just redirected the output to a file, which is fine if both the $TARGET_DIR and $TARGET_FILE exists. However, if one or both do not exist, then I still get a file created, but it's empty.
Things I've tried:
With $ret=system($cmd); and testing the the value of $ret:
  • Pre-fixing the cmd with set -o pipefail &&.
  • Adding set -o pipefail to the command run by ssh.
  • Adding set -o pipefail to the command run by sudo.
  • Doing the bzip2 locally.
    With @results = `$cmd`, and testing the value of $?:
  • Adding ; echo \${PIPESTATUS\@}; to the end of $cmd, within the string passed to ssh.
  • Adding ; echo \${PIPESTATUS\@}; to the end of $cmd, after the string passed to ssh.
    Using the @results approach, I only get one entry, so I suspect that the backtick method only sees one stream?

    Any ideas on how I can detect the remote pipeline failure?

    In reply to Re^3: best practices for checking system return values for piped commands? by Anonymous Monk
    in thread best practices for checking system return values for piped commands? by markjugg

    Title:
    Use:  <p> text here (a paragraph) </p>
    and:  <code> code here </code>
    to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.