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Carp(3) - carp, cluck, confess, croak, longmess, shortmess - return the message that carp and croak produce - man 3 Carp

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Carp(3)                Perl Programmers Reference Guide                Carp(3)



NAME
       carp    - warn of errors (from perspective of caller)

       cluck   - warn of errors with stack backtrace
                 (not exported by default)

       croak   - die of errors (from perspective of caller)

       confess - die of errors with stack backtrace

       shortmess - return the message that carp and croak produce

       longmess - return the message that cluck and confess produce

SYNOPSIS
           use Carp;
           croak "We're outta here!";

           use Carp qw(cluck);
           cluck "This is how we got here!";

           print FH Carp::shortmess("This will have caller's details added");
           print FH Carp::longmess("This will have stack backtrace added");

DESCRIPTION
       The Carp routines are useful in(1,8) your own modules because they act like
       die() or warn(), but with a message which is more likely to be useful
       to a user of your module.  In the case of cluck, confess, and longmess
       that context is a summary of every call in(1,8) the call-stack.  For a
       shorter message you can use carp, croak or shortmess which report the
       error(8,n) as being from where your module was called.  There is no guaran-
       tee that that is where the error(8,n) was, but it is a good educated guess.

       Here is a more complete description of how shortmess works.  What it
       does is search the call-stack for a function call stack where it hasn't
       been told that there shouldn't be an error.  If every call is marked
       safe, it then gives up and gives a full stack backtrace instead.  In
       other words it presumes that the first likely looking potential suspect
       is guilty.  Its rules for telling whether a call shouldn't generate
       errors work as follows:

       1.  Any call from a package to itself is safe.

       2.  Packages claim that there won't be errors on calls to or from pack-
           ages explicitly marked as safe by inclusion in(1,8) @CARP_NOT, or (if(3,n)
           that array is empty) @ISA.  The ability to override what @ISA says
           is new in(1,8) 5.8.

       3.  The trust in(1,8) item 2 is transitive.  If A trusts B, and B trusts C,
           then A trusts C.  So if(3,n) you do not override @ISA with @CARP_NOT,
           then this trust relationship is identical to, "inherits from".

       4.  Any call from an internal Perl module is safe.  (Nothing keeps user
           modules from marking themselves as internal to Perl, but this prac-
           tice is discouraged.)

       5.  Any call to Carp is safe.  (This rule is what keeps it from report-
           ing the error(8,n) where you call carp/croak/shortmess.)

       Forcing a Stack Trace

       As a debugging aid, you can force Carp to treat a croak as a confess
       and a carp as a cluck across all modules. In other words, force a
       detailed stack trace(3x,n,3x _nc_tracebits) to be given.  This can be very helpful when trying
       to understand why, or from where, a warning or error(8,n) is being gener-
       ated.

       This feature is enabled by 'importing' the non-existent symbol 'ver-
       bose'. You would typically enable it by saying

           perl -MCarp=verbose script.pl

       or by including the string(3,n) "MCarp=verbose" in(1,8) the PERL5OPT environment
       variable.

BUGS
       The Carp routines don't handle exception objects currently.  If called
       with a first argument that is a reference, they simply call die() or
       warn(), as appropriate.



perl v5.8.5                       2001-09-21                           Carp(3)

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