Re: Executing an application in Perl/CGI

Use and/&& to test againsts system since it returns 0 for successful and true value on failure.

system('some_command') && die 'cannot execute some_command';
# or
system 'some_command' and die 'cannot execute some_command';
[download]

Update: Fixed precedence and added another example with and. Thanks, kyle and blazar :-)

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Re^2: Executing an application in Perl/CGI by blazar (Canon) on May 22, 2007 at 19:34 UTC
`system 'some_command' && die 'cannot execute some_command';` [download] Really, both this and the OP's attempt get it wrong due to precedency issues. In fact I find myself repeating once again that as a rule of thumb, high precedence logical operators are for values and low precedence ones are for flow control. In particular, the OP's code appears to work because the die is never actually reached, while yours is the same as `system(die('cannot execute some_command'));` [download] So the program dies before calling system.	[reply] [d/l] [select]
Re^3: Executing an application in Perl/CGI by Anonymous Monk on May 22, 2007 at 19:38 UTC
Even with the fix the program still dies on the system call. It works perfectly fine but run in a web browser, it dies.	[reply]
Re^4: Executing an application in Perl/CGI by blazar (Canon) on May 22, 2007 at 19:42 UTC
Even with the fix the program still dies on the system call. It works perfectly fine but run in a web browser, it dies. Didn't `$!` and `$?` help?	[reply] [d/l] [select]
Re^2: Executing an application in Perl/CGI by kyle (Abbot) on May 22, 2007 at 19:33 UTC
`system 'some_command' && die 'cannot execute some_command';` This will always die because it's interpreted as: `system( 'some_command' && die 'cannot execute some_command' );` [download] Since the string `'some_command'` is a true value, the `die` always executes. To fix this, use `and`, which has a lower precedence: `system 'some_command' and die 'cannot execute some_command';` [download]	[reply] [d/l] [select]