Velocity Reviews - Computer Hardware Reviews

Velocity Reviews > Newsgroups > Programming > Perl > Perl Misc > FAQ 8.27 What's wrong with using backticks in a void context?

Reply
Thread Tools

FAQ 8.27 What's wrong with using backticks in a void context?

 
 
PerlFAQ Server
Guest
Posts: n/a
 
      03-28-2011
This is an excerpt from the latest version perlfaq8.pod, which
comes with the standard Perl distribution. These postings aim to
reduce the number of repeated questions as well as allow the community
to review and update the answers. The latest version of the complete
perlfaq is at http://faq.perl.org .

--------------------------------------------------------------------

8.27: What's wrong with using backticks in a void context?

Strictly speaking, nothing. Stylistically speaking, it's not a good way
to write maintainable code. Perl has several operators for running
external commands. Backticks are one; they collect the output from the
command for use in your program. The "system" function is another; it
doesn't do this.

Writing backticks in your program sends a clear message to the readers
of your code that you wanted to collect the output of the command. Why
send a clear message that isn't true?

Consider this line:

`cat /etc/termcap`;

You forgot to check $? to see whether the program even ran correctly.
Even if you wrote

print `cat /etc/termcap`;

this code could and probably should be written as

system("cat /etc/termcap") == 0
or die "cat program failed!";

which will echo the cat command's output as it is generated, instead of
waiting until the program has completed to print it out. It also checks
the return value.

"system" also provides direct control over whether shell wildcard
processing may take place, whereas backticks do not.



--------------------------------------------------------------------

The perlfaq-workers, a group of volunteers, maintain the perlfaq. They
are not necessarily experts in every domain where Perl might show up,
so please include as much information as possible and relevant in any
corrections. The perlfaq-workers also don't have access to every
operating system or platform, so please include relevant details for
corrections to examples that do not work on particular platforms.
Working code is greatly appreciated.

If you'd like to help maintain the perlfaq, see the details in
perlfaq.pod.
 
Reply With Quote
 
 
 
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
FAQ 6.22 What's wrong with using grep in a void context? PerlFAQ Server Perl Misc 0 02-21-2011 11:00 AM
What is the difference between void proba(); and void proba(void); ??? PencoOdStip@gmail.com C++ 1 05-23-2007 07:12 PM
what is the difference, void func(void) and void fucn() noblesantosh@yahoo.com C Programming 5 07-22-2005 04:38 PM
"void Method()" vs "void Method(void)" Ollej Reemt C++ 7 04-22-2005 03:47 AM
`void **' revisited: void *pop(void **root) Stig Brautaset C Programming 15 10-28-2003 09:03 AM



Advertisments