Re^2: best practices for checking system return values for piped commands?

I second the use of bash-es PIPESTATUS, I've used it in code like this:

my %cmds = ( 'bash' => '/usr/local/bin/bash',
             'gzip' => '/usr/bin/gzip',
             'lzop' => '/usr/bin/lzop',
             'wc'   => '/usr/bin/wc' );


my @zip_results = `$cmds{'bash'} -c '$cmds{$compress} -dc $file | $cmds{'wc'} -c ; echo \${PIPESTATUS\@}'`;

The last line of @zip_results has the status of both the 'compress' command and the 'wc' command.

Comment on Re^2: best practices for checking system return values for piped commands?

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Re^3: best practices for checking system return values for piped commands? by Anonymous Monk on Apr 08, 2009 at 07:33 UTC
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?	[reply] [d/l] [select]

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Re^3: best practices for checking system return values for piped commands?
by Anonymous Monk on Apr 08, 2009 at 07:33 UTC

ssh $TARGET_HOST "sudo find $TARGET_DIR -name \'$TARGET_FILE\' | sudo 
+cpio --create --format ustar" | bzip2 -9 -c
[download]

$TARGET_DIR

$TARGET_FILE

$ret=system($cmd);

$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?

[reply]
[d/l]
[select]