Php system() / exec() don't return output
It sounds like the program is outputting its warnings to standard error rather than standard output. exec
will only catch standard output. I don't know for certain that standard error is always sent to the apache error log, but it seems likely.
If you don't need compatibility with non-*nix systems, you can redirect standard error to standard output by appending 2>&1
to the command:
exec('some_command --option 2>&1', $output, $ret);
This should both make the warnings available to your php program and prevent unnecessary logging.
HappyDeveloper
Updated on June 04, 2022Comments
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HappyDeveloper almost 2 years
For common commands like 'ls', exec() works fine, eg:
exec('ls',$output,$retval); var_dump($output,$retval); // $output contains an array of filenames, and retval === 0
But when trying to execute another program, I can't get the output:
exec('some_command --a_parameter',$output,$retval); var_dump($output,$retval); // $output contains an empty array, end $retval === 0
This command prints some lines when executing it directly from the command-line though. I know the command has been successful because of the results (some files updated, data added, etc), and yet I can't see the output.
Any ideas?
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Khez almost 13 yearsDoes the command you issue actually print any output ?
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HappyDeveloper almost 13 yearsIt does when doing it directly from the command line. I mean I can see some lines of text appearing in the screen. Maybe there are different types of output?
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Charles almost 13 yearsWhat is the actual command you're running, please?
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HappyDeveloper almost 13 yearsits just a program I downloaded, not a linux thing
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D T over 9 yearsadd 2>&1 but output still is array empty, if execute from cmd , it output 2 values
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intuited over 9 yearsHmm could be that the command only outputs if its output is directed to a terminal. What are you trying to do?