3 ms·

Ask HN: Any ideas what code this is?

• psophis 12y ago
  Look like a regular expression.
• mc_hammer 12y ago
  $_ = 'somestring'; `$_`; // backticks are shell or exec(), $_ is the previous string. type echo "'^#(/||/@!@[{@:^[-['^";@@@\\>])@."."{)/];)^{";$,+=(++$,);$_.=">&$," to see what it does ;$,+=(++$,); looks like a for loop looks like php to me - backticks work in perl, bash and php
• edoceo 12y ago
  The $ vars lead me to either Shell, Perl or PHP. $_ is a special var in Bash and Perl. The '.' char is for string concat in Perl and PHP So, I think this is perl. The first statement evaluates to: "echo Brian Rogers >&2" The second statement `$_` runs that command. The end result is that this line of code prints: Brian Rogers
• andor 12y ago
  It's Perl. The last `$_`; evals what's in $_, so change it to just print the variable: $_='^#(/||/@!@[{@:^[-['^";@@@\\>])@.". "{)/];)^{";$,+=(++$,);$_.=">&$,"; print "$_"; The output is: echo Brian Rogers >&2
• jcr 12y ago
  Original Code $_='^#(/||/@!@[{@:^[-['^";@@@\\>])@.". "{)/];)^{";$,+=(++$,);$_.=">&$,";`$_`; $ man perlop = Assignment Operator. . Concatenation Operator. .= Concatenate and Assign. ^ Binary XOR. The binary "^" and "|" operators have lower precedence than relational operators like concatenate. ' Text between single quotes is an uninterpreted string. " Text between double quotes is an interpreted string. ; Statement terminator, just like C, java, javascript, ... $ man perlvar $_ The default input and pattern-searching space. A lot of perl code operates on this variable by default. $, The output field separator for the print operator. If defined, this value is printed between each of print's arguments. The default is "undef". The first statement is: $_='^#(/||/@!@[{@:^[-['^";@@@\\>])@."."{)/];)^{"; String1: '^#(/||/@!@[{@:^[-[' String2: ";@@@\\>])@." String3: "{)/];)^{" So we get: Result = String1 XOR String2 CONCAT String3 Since XOR has a lower precedence than Concatenate, we Concatenate first and then do the XOR. # First String: $_='^#(/||/@!@[{@:^[-['; printf "HEX1: %*v2.2X\n", ' ', $_; print "STR1: " . $_ . "\n"; $str1 = $_; # OUTPUT: # HEX1: 5E 23 28 2F 7C 7C 2F 40 21 40 5B 7B 40 3A 5E 5B 2D 5B # STR1: ^#(/||/@!@[{@:^[-[ # Second String: $_=";@@@\\>])@."; printf "HEX2: %*v2.2X\n", ' ', $_; print "STR2: " . $_ . "\n"; $str2 = $_; # OUTPUT: # HEX2: 3B 40 40 40 5C 3E 5D 29 40 2E # STR2: ;@@@\>])@. # Third String: $_="{)/];)^{"; printf "HEX3: %*v2.2X\n", ' ', $_; print "STR3: " . $_ . "\n"; $str3 = $_; # OUTPUT: # HEX3: 7B 29 2F 5D 3B 29 5E 7B # STR3: {)/];)^{ # Since the "^" binary XOR operator has lower precedence # than the "." concatenation operator, XOR str2 and str3 to # get the Fourth String: $_ = $str2 . $str3; printf "HEX4: %*v2.2X\n", ' ', $_; print "STR4: " . $_ . "\n"; $str4 = $_; # OUTPUT: # HEX4: 3B 40 40 40 5C 3E 5D 29 40 2E 7B 29 2F 5D 3B 29 5E 7B # STR4: ;@@@\>])@.{)/];)^{ # Now we can do a binary XOR on Sring #1 and String #4 to # get Fifth String: $_ = $str1 ^ $str4; printf "HEX5: %*v2.2X\n", ' ', $_; print "STR5: " . $_ . "\n"; $str5 = $_; # OUTPUT: # HEX5: 65 63 68 6F 20 42 72 69 61 6E 20 52 6F 67 65 72 73 20 # STR5: echo Brian Rogers # This is wickedly bad juju. The "(++$,)" portion increments an # undefined variable and would normally be an error, but with errors and # warnings shut off, it increments an undefined variable to 1, then adds # it to itself with "+=" to get 2. $,+=(++$,); # Here we concatenate shell redirection to stderr, which is file # descriptor 2, with the usual ">&2" since "$," now equals 2. $_.=">&$,"; print "\n"; printf "HEX-: %*v2.2X\n", ' ', $_; print "STR-: " . $_ . "\n"; # OUTPUT: # HEX-: 65 63 68 6F 20 42 72 69 61 6E 20 52 6F 67 65 72 73 20 3E 26 32 # STR-: echo Brian Rogers >&2 # Finally, the statement is evaluated in the shell: `$_`; Note: You should ask your friend Brian Rodgers if he always writes his name to Standard ERROR! ;)