[pgh-pm] system() not displaying scalar text

[Tom Moertel]

Matthew T. Engel wrote:
> [...] However, if I do a $ cat
> unicode_text_file | ./above_script.pl. I get blank lines where the 
> echo’d data should be.
> 
> I think the second file is Unicode because doing a $od –c Unicode_text 
> file, shows /0 in front of all the characters, and if I vi the same file 
> it shows ^@ before every character.

That's your problem.

Under the hood, arguments are passed to programs as traditional C-style, 
null-terminated strings.  (For more, read man page for the exec(3) 
system call: "const char *arg: a list of one or more pointers to 
null-terminated strings that represent the argument list available to 
the executed program.")  Therefore, when you pass an argument that 
contains a 0 byte to Perl's "system" function, the program that Perl 
invokes will see only the portion of the argument up to the 0, but 
nothing more.  For example:

     $ perl -e 'system "echo hi"'
     hi

     $ perl -e 'system "echo \0hi"'

     $

Cheers,
Tom