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perl, c program returns a negative value

Posted on 2012-09-12
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Last Modified: 2012-09-28
I have a perl program that calls a c program.  When I print $return_val, I don't get the same number that the my_c_program returned.  my_c_program returns negative and positive number.

my $return_val = '/tmp/my_c_program';
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Question by:rgbcof
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by:ozo
ID: 38393703
my $return_val = '/tmp/my_c_program';
does not call a c program, it assigns a literal string to $return_val

If you had
my $return_val = `/tmp/my_c_program`;
then $return_val would contain whatever was printed to STDOUT by the execution of /tmp/my_c_program
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Carl Bohman earned 1500 total points
ID: 38405971
If you are looking for the actual return code, you need to use the special $? variable.
my $StandardOutput =`/path/to/your/command with options`;
my $ReturnCode = $? >> 8;

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Note that you need to bit-shift the return code as I did to get the "normal" return code that you might get via a shell script (for example).  The extra bits are flags that include information such as whether a core file was generated or not.  In most cases, you don't need those bits if you just want to see whether the command returned zero or not.
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