Full Discussion: ksh bug?
Top Forums UNIX for Advanced & Expert Users ksh bug? Post 302876068 by alister on Thursday 21st of November 2013 02:22:26 PM
Quote:
Originally Posted by MadeInGermany
Then let's call it a shortcoming.
It looks like -x mode uses stderr, and can conflict with redirection in the shell code.
It can get messy, yes.

This is also an issue for bash ...
Code:
$ bash -xc 'echo foo; exec 2>&1; echo bar' > stdout
+ echo foo
+ exec
$ cat stdout
foo
+ echo bar
bar

... but since it does not trace redirections, the destination of the trace won't change mid-command.

Quote:
Originally Posted by MadeInGermany
Then, why stderr and not another file descriptor?
I would assume because stderr is known to be reserved for diagnostic and error messages, not data. If an alternative file descriptor were chosen, the possibility for a collision would still exist.

Corona688 makes an excellent point:
Quote:
Originally Posted by Corona688
Being 'clever' about it would make obvious things, like redirecting a trace's output into a file, difficult.
Cleverness would include attempting to detect and handle a collision between the internal tracing descriptor and a script's redirections.

Regards,
Alister

Last edited by alister; 11-21-2013 at 03:36 PM..
 
Test Your Knowledge in Computers #894
Difficulty: Medium
A tr command is also part of ASCII's MSX-DOS2 Tools for MSX-DOS version 2.
True or False?

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GET_CLASS(3)								 1							      GET_CLASS(3)

get_class - Returns the name of the class of an object

SYNOPSIS
string get_class NULL ([object $object]) DESCRIPTION
Gets the name of the class of the given $object. PARAMETERS
o $object - The tested object. This parameter may be omitted when inside a class. RETURN VALUES
Returns the name of the class of which $object is an instance. Returns FALSE if $object is not an object. If $object is omitted when inside a class, the name of that class is returned. ERRORS
/EXCEPTIONS If get_class(3) is called with anything other than an object, an E_WARNING level error is raised. CHANGELOG
+--------+---------------------------------------------------+ |Version | | | | | | | Description | | | | +--------+---------------------------------------------------+ | 5.3.0 | | | | | | | | | | NULL became the default value for $object, so | | | passing NULL to $object now has the same result | | | as not passing any value. | | | | | 5.0.0 | | | | | | | The class name is returned in its original nota- | | | tion. | | | | | 5.0.0 | | | | | | | The $object parameter is optional if called from | | | the object's method. | | | | +--------+---------------------------------------------------+ EXAMPLES
Example #1 Using get_class(3) <?php class foo { function name() { echo "My name is " , get_class($this) , " "; } } // create an object $bar = new foo(); // external call echo "Its name is " , get_class($bar) , " "; // internal call $bar->name(); ?> The above example will output: Its name is foo My name is foo Example #2 Using get_class(3) in superclass <?php abstract class bar { public function __construct() { var_dump(get_class($this)); var_dump(get_class()); } } class foo extends bar { } new foo; ?> The above example will output: string(3) "foo" string(3) "bar" SEE ALSO
get_called_class(3), get_parent_class(3), gettype(3), is_subclass_of(3). PHP Documentation Group GET_CLASS(3)

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