Programming Perl, 4th Edition

oct

oct EXPR
oct

This function interprets EXPR as an octal string and returns the equivalent decimal value. If EXPR happens to start with “0x”, it is interpreted as a hexadecimal string instead. If EXPR starts off with “0b”, it is interpreted as a string of binary digits. The following will properly convert to whole numbers input strings in decimal, binary, octal, and hex bases using standard Perl notation:

$val = oct $val if $val =~ /^0/;

For the inverse function, use sprintf with an appropriate format:

$dec_perms = (stat("filename"))[2] & 07777;
$oct_perm_str = sprintf "%o", $dec_perms;

The oct function is commonly used when a data string such as “644” needs to be converted into a file mode, for example. Although Perl automatically converts strings into numbers as needed, this automatic conversion assumes base 10.

Leading whitespace is ignored without warning, as are any trailing nondigits, such as a decimal point (oct only handles nonnegative integers, not negative integers or floating point).