|Perl Language Reference Manual|
by Larry Wall and others
Paperback (6"x9"), 724 pages
RRP £29.95 ($39.95)
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Contains the name of the program being executed.
On some (read: not all) operating systems assigning to
the argument area that the
ps program sees. On some platforms you
may have to use special
ps options or a different
ps to see the
changes. Modifying the $0 is more useful as a way of indicating the
current program state than it is for hiding the program you're
running. (Mnemonic: same as sh and ksh.)
Note that there are platform specific limitations on the maximum
$0. In the most extreme case it may be limited to the
space occupied by the original
In some platforms there may be arbitrary amount of padding, for
example space characters, after the modified name as shown by
In some platforms this padding may extend all the way to the original
length of the argument area, no matter what you do (this is the case
for example with Linux 2.2).
Note for BSD users: setting
$0 does not completely remove "perl"
from the ps(1) output. For example, setting
"perl: foobar (perl)" (whether both the
"perl: " prefix
and the " (perl)" suffix are shown depends on your exact BSD variant
and version). This is an operating system feature, Perl cannot help it.
In multithreaded scripts Perl coordinates the threads so that any
thread may modify its copy of the
$0 and the change becomes visible
to ps(1) (assuming the operating system plays along). Note that
the view of
$0 the other threads have will not change since they
have their own copies of it.
If the program has been given to perl via the switches
$0 will contain the string
|ISBN 9781906966027||Perl Language Reference Manual||See the print edition|