When representing numeric literal values, Perl has a simple rule: Integers integers that are prefixed with one or more leading zeroes are interpreted as octal, and integers with no leading zero are interpreted as decimal.
While simple, this rule is not known among many developers , and is not obvious to those unware unaware of it. Consequently, do not prefix an integer with leading zeros. If it is to be interpreted as octal, use the oct() function, which clearly indicates the number to be treated as octal.
| Code Block | ||
|---|---|---|
| ||
my $perm1 = 0644; # noncompliant, octal my $perm2 = "0644"; # noncompliant, decimal my $perm3 = oct("644"); # compliant, octal my $perm4 = 644; # compliant, decimal |
...
Tool | Diagnostic |
|---|---|
Perl::Critic | ValuesAndExpressions::ProhibitLeadingZeros |
B::Lint | Illegal octal digit.* |
Bibliography
| [Conway 2005] | "Leading Zeroes," p. 58 |
| [CPAN] | Elliot Shank, Perl-Critic-1.116 ValuesAndExpressions::ProhibitLeadingZeros |
...
[Conway 2005], pg. 58. "Leading Zeroes"
02. Expressions [!CERT Perl
Secure Coding Standard^button_arrow_right.png!|EXP31-PL. Do not use the two-argument form of open()]