Introduction to Sybase, Part 2
All of the programs here are available for download. If you type in these programs, be sure to use chmod to make them executable.
Writing a sybperl program is quite simple. Listing 1 is our first example program. This will list the names of all the databases in the server. Here is a line-by-line explanation of the program.
Line 1 tells Linux which program to use to run this script. This must be the new version of Perl you just installed. Make sure you change this line to point to the correct version of Perl on your system.
Line 3 tells Perl to use the CT-library interface to Sybase. It should be at the beginning of all Perl scripts you write that access a Sybase server.
Line 5 attaches to the correct Sybase server. The first parameter is the user name, the second is the password and the third is the name of the server.
Line 7 is the SQL to run.
Lines 9-10 are commands that run the query on the server and return a reference to an array of rows, @rows. Note this command loads the entire result set into memory. This is fine for small result sets, but if you are expecting a large result set, you shouldn't use ct_sql. Later, I will give you an alternative method for executing commands and receiving large result sets.
Lines 12-14 will print all rows that were returned.
Listing 2 is an example of a sybperl program that updates data. In Line 7, we use the same ct_sql command to send the SQL to the database, except this time a set of rows is not returned. The insert, delete and update SQL commands also do not return rows. The SQL command use pubs2 tells Sybase to make the pubs2 database the default database for the rest of this session. In Line 10, we again use the ct_sql command to run the SQL. This time, we add a row to the discounts table. You can use the isql program to run an SQL SELECT command to verify that the row was added.
Linux is mostly used as a web server, and Perl is primarily used to write web applications. So, we will create a Perl program to access the Sybase database.
Writing a CGI program to access Sybase is quite simple. Listing 3 is the complete code of a CGI program to let you know who's logged in to your Sybase server. Place this program in your web server's cgi-bin directory. On a default Red Hat system, the directory is /home/httpd/cgi-bin/. For this example, name the program listing3.pl.
In lines 5 and 6, we set two environment variables. The Sybase DB-Library and CT-Library must find these environment variables, or an error will occur. When you run a CGI program, very few environment variables are passed to your program. These two environment variables must be set in each CGI program that needs to access Sybase. If you have many CGI programs, place these commands in a file included in all your CGI programs.
The SYBASE environment variable contains the directory of the Sybase software. The DSQUERY variable contains the name of the default server.
The only other difference between this example and the others is it outputs HTML to a browser.
These example programs show the basics of accessing a Sybase database server. In production programs, a few more things must be taken care of in your programs.
Errors from the server must be handled properly. If you ignore them, your program will stop when it encounters a server error.
In all our example programs, ct_sql was used to run queries. It works fine for SQL commands and stored procedures which don't return result sets, but would have severe problems for queries returning large result sets.
Listing 4 shows how to handle errors and demonstrate a replacement for the ct_sql command. In lines 3 and 4, we establish both a client and a server message call-back routine. These routines will be called when the server or client generates an informational or error message.
In lines 7-20, we handle a single SQL statement. Sybase allows a single statement to return multiple result sets. Lines 8-10 will process each result set. Lines 17-19 will handle each row in a result set. Lines 11-16 will look at the result set and print the names and types of each column. A Sybase result set contains more than just data—it also includes column definition information.
Lines 23-50 are the two call-back routines. These routines are called each time there is a message from the server or client. An example of a client message is the one returned if you can't log in to the server. An example of a server message is the one returned if you have an error in your SQL.
All this information can be found within the sybperl and the Sybase documentation.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
Free to Linux Journal readers.Register Now!
- Stunnel Security for Oracle
- SourceClear Open
- SUSE LLC's SUSE Manager
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- My +1 Sword of Productivity
- Managing Linux Using Puppet
- Tech Tip: Really Simple HTTP Server with Python
- Non-Linux FOSS: Caffeine!
- Google's SwiftShader Released
- Doing for User Space What We Did for Kernel Space
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide