Exercise: login to cowboy.cns.uni.edu and try the
which perl
command to see what the output is.
chmod 755 myFile.txt
ls -l myFile.txt
-rwxr-xr-x myFile.txt
chmod 644 myFile.txt
ls -l myFile.txt
-rw-r--r-- myFile.txt
In octal (base 8) and in binary (base 2) we have Octal Binary ls -l
0 000 ---
1 001 --x
2 010 -w-
3 011 -wx
4 100 r--
5 101 r-x
6 110 rw-
7 111 rwx
--- --- ---
rwx 421
As stated on page 292 of Elizabeth Castro book,
you assign a value of 4 for read permission,
2 for write permission, and
1 for execute permission.
Saying chmod 755 fileName.txt means you are giving all permissions
to yourself (the owner of fileName.txt),
since 7 = 4 + 2 + 1 = 111 in binary.
You are giving read and execute permissions
to your group and everyone else (others),
because 4 = read and 1 = execute, and
4 + 1 = 5 and 5 = 101 in binary, or r-x
101
Here is the statement we looked at in randomGenX.cgi PERL script:
$quoteList =~ tr/ //d;
The user could type in 1, 5 - 7 , 9
and it would be transliterated
to 1,5-7,9
by the $quoteList =~ tr/ //d;
statement.
The d stands for delete.
---------------------------------------------------------------------
What would the following PERL statements do?
print "Please enter data to be processed by the transliteration " .
"function: \n\n";
$someData = <>;
print "\nYou entered: $someData";
$someData =~ tr/a-z/b-za/;
print "\n It is now: $someData\n\n";
Please enter data to be processed by the transliteration function: UNI Panthers rock and roll, especially volleyball! Feb 19th, 2003 You entered: UNI Panthers rock and roll, especially volleyball! Feb 19th, 2003 It is now: UNI Pbouifst spdl boe spmm, ftqfdjbmmz wpmmfzcbmm! Ffc 19ui, 2003
use CGI qw(:standard);
$quoteList = param('quoteNumbers');