23
Sat, Nov
1 New Articles

Retrieving the Directory Contents of an FTP Server from Within RPG

RPG
Typography
  • Smaller Small Medium Big Bigger
  • Default Helvetica Segoe Georgia Times

Create an RPG program to retrieve a list of existing files on an FTP server.

 

In a previous article, I discussed how to upload a file to an FTP server and how to automate the process using RPG in a manner that would allow your program to evolve to easily support future modifications and server additions and changes. In this article, I'll discuss how you can retrieve information from an FTP server and use that information to download files.

Verifying FTP Server Access from the IBM i

As I mentioned in my previous article, you should test out your file transfer interactively prior to automating your FTP process. For this example, we will be listing the contents of a directory on a fictitious FTP server:

 

 

Fictitious Target FTP Server Information

Target FTP Server

ftp.example.com

User Name

tomsnyder

Password

mcpress

 

Testing the FTP process interactively will ensure that the IBM i has access to the server and that the user name and password are active on the target server. You can do this by typing FTP or STRTCPFTP on the command line and prompting it to enter the DNS name or IP address of the server, or you can enter the FTP server information with this command:

 

FTP RMTSYS('ftp.example.com')

 

or

 

STRTCPFTP RMTSYS('ftp.example.com')

 

Once you have successfully connected to the FTP server, you will enter your user name and password interactively.

 

Interactively Retrieving the Directory List from the FTP Server

 

To retrieve the contents of the directory list, we will use the DIR command on the FTP server that we are connected to. If you used the DIR command alone, it would list the directory contents to the screen. But there is a (DISK option that we will usr with the DIR command to download the list to a physical file.

 

USER PWD

dir (DISK

close

quit

 

When you execute the dir (DISK command, the directory contents of the location that your profile has access to on the server will be downloaded into the DIROUTPUT member of the DIROUTPUT file in your current library.

Retrieving the Directory List from the FTP Server in Batch

 

Now that we have verified that we can successfully download the directory list into a physical file, we can automate the process by reusing the program that we created in the previous article. For this article, we will refer to the previous program as FTPPGM.

 

The FTPPGM will use the FTPINPUT file, which will be overridden to be the INPUT file that is expected for use with the STRTCPFTP command. The FTPINPUT file will be a physical file containing a single field that will contain the commands to be sequentially executed by STRTCPFTP.

 

For this example, we will create a new member in the FTPINPUT file named MCP_DIR. The MCP_DIR member will contain the user name and password in the first record; the rest of the commands are listed above when the FTP was executed interactively:

 

tomsnyder mcpress

dir (DISK

close

quit

 

Overriding the DIROUTPUT File

 

The first thing I would like to do is override the DIROUTPUT file to put it into its own member. This will help to avoid creating file locks and/or inadvertently overwriting your expected data when another directory listing program is running at the same time. No problem: just create a physical file with a field large enough to accommodate the file information and override it to the member that you would like to use. I displayed the file description for DIROUTPUT to be 256 characters, so I made FTPOUTPUT the same size. For this example, we will be using the MCP_DIR member of a new file named FTPOUTPUT. You could get more creative by using the job name or whatever you would feel adequate to avoid file locks with other concurrent jobs. Here is the DDS we'll use for that file:

 

A          R FTPFMT2

A            FTPOUT       256

 

Overlaying Fields onto the File Information

 

When you download the directory listing into your FTPOUTPUT file, you will probably want to overlay some fields onto the data to separate the information into usable data. I am sure that with all the different operating systems and FTP servers that you support, as I do, you may find differences between the data results of an IBM i versus Windows, UNIX, Linux, or a Mac, and you may have to tweak your overlays, but I have found this one to work for most cases.

 

DXFTPOUTPUT       E DS                  EXTNAME(FTPOUTPUT)

D FOFILEDATE              1      8

D FOFILETIME             11     17

D FOFILEDATIM             1     17

D FOFILEDIR              25     29

D FOFILESIZE             29     38

D FOFILENAME             40     89

D FOMACFNAME             49     98

 

One solution to supporting multiple operating systems would be to expand the FTPSERVERS file that contains the server information to include the operating system of the FTP server to determine which overlay template to use. You can see that there is a FOMACFNAME field defined that I use for file names on Macintosh FTP servers.

The Code

 

At this point, we have tested the FTP commands interactively, created a data structure to overlay the results of the FTP DIR command, populated our FTPINPUT file to contain the commands that will be executed in batch, and successfully downloaded the directory listing into our FTPOUTPUT file. Now we can use this information to create a basic RPG program that will utilize these resources and that can be used as a starting point for more-complex implementations. In order to do this, we will reuse the application that was created in the previous FTP article to execute the commands. Then we will read through the data that was downloaded using the DIR (DISK command.

 

FFTPOUTPUT IF   E           K DISK    USROPN

D**********************************************************************

DARGS             DS

D ARGSITE                       10A

D ARGJOB                        10A

D* Field Overlays onto DIR results in FTPOUTPUT file.

D XFTPOUTPUT    E DS                  EXTNAME(FTPOUTPUT)

D  FOFILEDATE             1      8

D  FOFILETIME            11     17

D  FOFILEDATIM            1     17

D  FOFILEDIR             25     29

D  FOFILESIZE            29     38

D  FOFILENAME            40     89

D  FOMACFNAME            49     98

D* Prototype for QCMDEXC

D ExecuteCommand...

D                 PR                  extPgm('QCMDEXC')

D  argInCommand              65535A   const options(*varsize)

D  argInLength                  15P 5 const

D*

D cmd             S           1024A

D displayBytes    S             52A

D*

C/EJECT

C     *ENTRY        PLIST

C                   PARM                    ARGS

/free

// Change the current library for DIROUTPUT

cmd = 'CHGCURLIB CURLIB(MYLIB)';

ExecuteCommand(%trim(CMD):%len(%trim(CMD)));

// Override the DIROUTPUT file Member

cmd = 'OVRDBF FILE(DIROUTPUT)'

+ ' TOFILE(DIROUTPUT)'

+ ' MBR(' + %TRIM(ARGJOB) + ')';

ExecuteCommand(%trim(CMD):%len(%trim(CMD)));

// Execute the FTP commands to download the directory list

// This is the program discussed in the previous FTP article

cmd = 'CALL FTPPGM ''SCRANTON  MCP_DIR''';

ExecuteCommand(%trim(CMD):%len(%trim(CMD)));

// Copy the DIROUTPUT file to FTPOUTPUT

cmd = 'CPYF FROMFILE(DIROUTPUT)'

+ ' TOFILE(FTPOUTPUT)'

+ ' FROMMBR(' + %TRIM(ARGJOB) + ')'

+ ' TOMBR(' + %TRIM(ARGJOB) + ')'

+ ' MBROPT(*REPLACE) FMTOPT(*NOCHK)';

ExecuteCommand(%trim(CMD):%len(%trim(CMD)));

// Override the DIROUTPUT file Member

cmd = 'OVRDBF FILE(FTPOUTPUT)'

+ ' TOFILE(FTPOUTPUT)'

+ ' MBR(' + %TRIM(ARGJOB) + ')';

ExecuteCommand(%trim(CMD):%len(%trim(CMD)));

open FTPOUTPUT;

read FTPOUTPUT;

dow not %eof(FTPOUTPUT);

displayBytes = 'File: '

+ %trim(FOFILENAME) + ' '

+ %trim(FOFILEDATIM);

dsply displayBytes;

read FTPOUTPUT;

enddo;

close FTPOUTPUT;

*inlr = *ON;

/end-free

 

This program will demonstrate how to get the basic functionality working. With this foundation, you could reuse the logic in batch to verify file transfers, retrieve file lists to assist with errors associated with missing files on a Web server for XML feeds, or automatically perform administrative tasks on remote servers.

 

You could also use this logic for interactive programs to allow users to view and perform transfers on files that are located on remote servers. This can be done simply by writing the contents to a display file and providing some options for actions to be performed. If you were to allow navigation through the folders, you could simply repopulate the FTPINPUT file within your program, resubmit the call to the FTPPGM with the new FTPINPUT file to execute the desired commands, and then repopulate the subfile with the results.

 

Download the Code

 

You can download the code used in this article--as well as the fixed-format version--by clicking here.

 

More Information

 

For more information on FTP on the IBM i, you can find a PDF about FTP on the IBM Web site that contains additional information on the FTP DIR command.

 

Thomas Snyder

Thomas Snyder has a diverse spectrum of programming experience encompassing IBM technologies, open source, Apple, and Microsoft and using these technologies with applications on the server, on the web, or on mobile devices.

Tom has more than 20 years' experience as a software developer in various environments, primarily in RPG, Java, C#, and PHP. He holds certifications in Java from Sun and PHP from Zend. Prior to software development, Tom worked as a hardware engineer at Intel. He is a proud United States Naval Veteran Submariner who served aboard the USS Whale SSN638 submarine.

Tom is the bestselling author of Advanced, Integrated RPG, which covers the latest programming techniques for RPG ILE and Java to use open-source technologies. His latest book, co-written with Vedish Shah, is Extract, Transform, and Load with SQL Server Integration Services.

Originally from and currently residing in Scranton, Pennsylvania, Tom is currently involved in a mobile application startup company, JoltRabbit LLC.


MC Press books written by Thomas Snyder available now on the MC Press Bookstore.

Advanced, Integrated RPG Advanced, Integrated RPG
See how to take advantage of the latest technologies from within existing RPG applications.
List Price $79.95

Now On Sale

Extract, Transform, and Load with SQL Server Integration Services Extract, Transform, and Load with SQL Server Integration Services
Learn how to implement Microsoft’s SQL Server Integration Services for business applications.
List Price $79.95

Now On Sale

BLOG COMMENTS POWERED BY DISQUS

LATEST COMMENTS

Support MC Press Online

$

Book Reviews

Resource Center

  • SB Profound WC 5536 Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application. You can find Part 1 here. In Part 2 of our free Node.js Webinar Series, Brian May teaches you the different tooling options available for writing code, debugging, and using Git for version control. Brian will briefly discuss the different tools available, and demonstrate his preferred setup for Node development on IBM i or any platform. Attend this webinar to learn:

  • SB Profound WP 5539More than ever, there is a demand for IT to deliver innovation. Your IBM i has been an essential part of your business operations for years. However, your organization may struggle to maintain the current system and implement new projects. The thousands of customers we've worked with and surveyed state that expectations regarding the digital footprint and vision of the company are not aligned with the current IT environment.

  • SB HelpSystems ROBOT Generic IBM announced the E1080 servers using the latest Power10 processor in September 2021. The most powerful processor from IBM to date, Power10 is designed to handle the demands of doing business in today’s high-tech atmosphere, including running cloud applications, supporting big data, and managing AI workloads. But what does Power10 mean for your data center? In this recorded webinar, IBMers Dan Sundt and Dylan Boday join IBM Power Champion Tom Huntington for a discussion on why Power10 technology is the right strategic investment if you run IBM i, AIX, or Linux. In this action-packed hour, Tom will share trends from the IBM i and AIX user communities while Dan and Dylan dive into the tech specs for key hardware, including:

  • Magic MarkTRY the one package that solves all your document design and printing challenges on all your platforms. Produce bar code labels, electronic forms, ad hoc reports, and RFID tags – without programming! MarkMagic is the only document design and print solution that combines report writing, WYSIWYG label and forms design, and conditional printing in one integrated product. Make sure your data survives when catastrophe hits. Request your trial now!  Request Now.

  • SB HelpSystems ROBOT GenericForms of ransomware has been around for over 30 years, and with more and more organizations suffering attacks each year, it continues to endure. What has made ransomware such a durable threat and what is the best way to combat it? In order to prevent ransomware, organizations must first understand how it works.

  • SB HelpSystems ROBOT GenericIT security is a top priority for businesses around the world, but most IBM i pros don’t know where to begin—and most cybersecurity experts don’t know IBM i. In this session, Robin Tatam explores the business impact of lax IBM i security, the top vulnerabilities putting IBM i at risk, and the steps you can take to protect your organization. If you’re looking to avoid unexpected downtime or corrupted data, you don’t want to miss this session.

  • SB HelpSystems ROBOT GenericCan you trust all of your users all of the time? A typical end user receives 16 malicious emails each month, but only 17 percent of these phishing campaigns are reported to IT. Once an attack is underway, most organizations won’t discover the breach until six months later. A staggering amount of damage can occur in that time. Despite these risks, 93 percent of organizations are leaving their IBM i systems vulnerable to cybercrime. In this on-demand webinar, IBM i security experts Robin Tatam and Sandi Moore will reveal:

  • FORTRA Disaster protection is vital to every business. Yet, it often consists of patched together procedures that are prone to error. From automatic backups to data encryption to media management, Robot automates the routine (yet often complex) tasks of iSeries backup and recovery, saving you time and money and making the process safer and more reliable. Automate your backups with the Robot Backup and Recovery Solution. Key features include:

  • FORTRAManaging messages on your IBM i can be more than a full-time job if you have to do it manually. Messages need a response and resources must be monitored—often over multiple systems and across platforms. How can you be sure you won’t miss important system events? Automate your message center with the Robot Message Management Solution. Key features include:

  • FORTRAThe thought of printing, distributing, and storing iSeries reports manually may reduce you to tears. Paper and labor costs associated with report generation can spiral out of control. Mountains of paper threaten to swamp your files. Robot automates report bursting, distribution, bundling, and archiving, and offers secure, selective online report viewing. Manage your reports with the Robot Report Management Solution. Key features include:

  • FORTRAFor over 30 years, Robot has been a leader in systems management for IBM i. With batch job creation and scheduling at its core, the Robot Job Scheduling Solution reduces the opportunity for human error and helps you maintain service levels, automating even the biggest, most complex runbooks. Manage your job schedule with the Robot Job Scheduling Solution. Key features include:

  • LANSA Business users want new applications now. Market and regulatory pressures require faster application updates and delivery into production. Your IBM i developers may be approaching retirement, and you see no sure way to fill their positions with experienced developers. In addition, you may be caught between maintaining your existing applications and the uncertainty of moving to something new.

  • LANSAWhen it comes to creating your business applications, there are hundreds of coding platforms and programming languages to choose from. These options range from very complex traditional programming languages to Low-Code platforms where sometimes no traditional coding experience is needed. Download our whitepaper, The Power of Writing Code in a Low-Code Solution, and:

  • LANSASupply Chain is becoming increasingly complex and unpredictable. From raw materials for manufacturing to food supply chains, the journey from source to production to delivery to consumers is marred with inefficiencies, manual processes, shortages, recalls, counterfeits, and scandals. In this webinar, we discuss how:

  • The MC Resource Centers bring you the widest selection of white papers, trial software, and on-demand webcasts for you to choose from. >> Review the list of White Papers, Trial Software or On-Demand Webcast at the MC Press Resource Center. >> Add the items to yru Cart and complet he checkout process and submit

  • Profound Logic Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application.

  • SB Profound WC 5536Join us for this hour-long webcast that will explore:

  • Fortra IT managers hoping to find new IBM i talent are discovering that the pool of experienced RPG programmers and operators or administrators with intimate knowledge of the operating system and the applications that run on it is small. This begs the question: How will you manage the platform that supports such a big part of your business? This guide offers strategies and software suggestions to help you plan IT staffing and resources and smooth the transition after your AS/400 talent retires. Read on to learn: