TechTip: Talk to the Internet with cURL

Get cURL

Some kind souls on the Web have compiled and packaged the AIX binary for us, so we don't have to compile our own. For this demonstration, we'll choose a non-SSL-enabled version of cURL (SSL encryption would require installing many prerequisites).

Download the cURL command-line binary. It is archived at UCLA's Public Domain Software Library for AIX. Choose the download from the Binary column where the row shows AIX=4.2 and Version=7.13.1. Although this package is somewhat old, it is more complete than that supplied for newer versions. The file can also be downloaded directly (this could change over time) from ftp://aixpdslib.seas.ucla.edu/pub/curl/RISC/4.2/exec/curl.7.13.1.tar.Z. The ".tar.z" extension indicates a UNIX-style compressed archive file. Save the file to your hard drive.

Extract and Install cURL

Although you could use PASE's uncompress/tar commands on your iSeries/i5 to extract the contents of the ".tar.z" file, I prefer to extract the files on my Windows PC with a program such as the free ZipGenius.

The extracted contents comprise a directory structure. Of that structure, we are interested in the /usr/local/bin folder. Look inside the bin folder for a file called curl. Copy curl to your i5's root file system. I chose to copy curl to a folder called /coolprograms using a Windows Explorer mapped drive. If I had not been able to map a drive for some reason, I could have used iSeries Navigator or FTP.

Get a Web Page

Let's try it!

Launch the PASE interactive (terminal) environment:
CALL QP2TERM

Once inside PASE:
cd /coolprograms [or whatever folder you copied curl into]
curl www.google.com

If the i5 is connected to the Internet, you will see the output on your screen (Figure 1).

Figure 1: The command curl www.google.com retrieves the HTML of Google's home page. (Click images to enlarge.)

Redirect the Output to a File

We may wish to redirect cURL's output to a file for later analysis or other use. In our example, we will create an output directory and then adapt our curl command to send the output there. A redirection symbol (>) sends the HTML to a file of our choice.

mkdir /htmloutput
curl www.google.com > /htmloutput/google.html

Verify the successful download by viewing the contents with UNIX's cat command:
cat /htmloutput/google.html

The results of these commands are shown in Figure 2.

Figure 2: cURL sends output to a file whose contents are then displayed by the UNIX cat command.

Automate cURL by Calling It from CL

For ultimate control, we can automate cURL by calling it via QP2SHELL or QP2SHELL2 from our CL programs:
/* The -o means we will indicate where to save our result. */
/* The -s means silent mode: Do not show status or errors. */
/* (Note that the -o and -s arguments must be lowercase) */

CALL PGM(QP2SHELL2) +
PARM('/coolprograms/curl' '-o' +
'/htmloutput/webpage.html' +
'http://www.thesite.com' '-s')

Use this CL command as a template for many possibilities of letting your i5 talk to the Internet.

Resources

Manual Page for cURL
Using cURL to Automate HTTP Jobs
Mailing Lists for cURL
History of cURL by its creator, Daniel Stenberg

Alan Seiden is Senior Developer and Technical Lead at Strategic Business Systems, Inc., in Ramsey, New Jersey, where he helps clients reach their business goals using IBM i5, Microsoft, and open-source technology, with an emphasis on usability. Alan is an advisory board member of the New York City Usability Professionals Association. Contact Alan at alanseiden@acm.org.

Alan Seiden
		About the Author:
		Alan Seiden enjoys leading collaborative software projects and troubleshooting clients' perplexing problems. He has written many articles for usability and IT publications. Alan is vice president of the New York City Usability Professionals Association and a member of New York PHP.
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