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Re^3: caller() mystery

by ikegami (Pope)
on Sep 26, 2008 at 10:23 UTC ( #713847=note: print w/replies, xml ) Need Help??


in reply to Re^2: caller() mystery
in thread caller() mystery

caller(0) returns info about _format_caller's caller.
caller(1) returns info about f's caller
caller(2) would return info about the main program's caller, but that's no longer in Perl. What are you expecting it to return?

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Re^4: caller() mystery
by rovf (Priest) on Sep 26, 2008 at 10:41 UTC
    Update Please disregard this posting. I finally understood the issue (see id:://713852).
    caller(1) returns info about f's caller

    If this is the case, I would understand why my approach failed. But then I don't understand why in my original program, caller(1) (executed from within _format_caller) delivered

    main,U:\develsv\ARTS\playground\callertest.pl,16,main::f,1,,,,2,UUUUUU +UUUUU
    That is, it says "the caller is main::f". This is _format_caller's caller, NOT f's caller. Actually that's why I had concluded that counting would start at 1. And indeed, from the command line:

    perl -lwe 'sub a{print((caller 0)[3])};sub b{a()};sub c{b()}; c'
    gives main::a (that is, caller 0 says "who I am", i.e. which function is invoking caller).
    perl -lwe 'sub a{print((caller 1)[3])};sub b{a()};sub c{b()}; c'
    gives main::b (that is, caller 1 says who has called me)
    perl -lwe 'sub a{print((caller 2)[3])};sub b{a()};sub c{b()}; c'
    gives main::c (that is, the caller of main::b), but for
    perl -lwe 'sub a{print((caller 3)[3])};sub b{a()};sub c{b()}; c'
    I would have expected to get information about the caller of main::c, which is the main program (not the shell), but there is none.

    -- 
    Ronald Fischer <ynnor@mm.st>
      that is, caller 0 says "who I am", i.e. which function is invoking caller

      No, you are incorrect.

      caller() doesn't return which 'function' calls you - it returns the package name, the file name and the line number of the caller; which is in the first three arguments. All the other arguments have to do how you are called. So, caller(0)[3] returns how you were called as.

      If you want to find out which function called you (if there is such a function), you call caller(1), which gives you information how your caller is called.

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