Zipping files in the IFS

The information that went into creating this post was provided by Al Bernard. Al is an experienced IBM i (AS400) developer and colleague. In a recent conversation he mentioned to me something he had done that I have not.

He was asked to create a download file that would be emailed to a group of people. The file was so large that the Administrator of the email servers asked if the file could be zipped, to reduce its size, and then sent. My present employer uses a third party tool to send email from the IBM i, and I will not be discussing that here. What I will be discussing is the way he copied the file to the IFS and zipped it. Then I will describe how to do the reverse, taking the zipped file and putting the data into a DDS file.

Before you attempt this for yourself you will need a folder in the IFS you can use. If you do not have one you can use either create it for yourself or ask your IBM i Administrator to do so for you. In this post I will use the name MyFolder for my folder.

The extracted data has been output to a file that I will call EXTRACT and it is in my library, MYLIB.

First I needed to get the data from the file EXTRACT into the IFS as a CSV (Comma Seperated Values) file. This I do using the Copy To Import File, CPYTOIMPF, command, see below.

CPYTOIMPF FROMFILE(MYLIB/EXTRACT) + TOSTMF('MyFolder/extract.csv') + MBROPT(*REPLACE) + STMFCCSID(*STDASCII) + RCDDLM(*CRLF)

The first two parameters of the command define where the file is, MYLIB/EXTRACT, and where you want it to go, into the folder MyFolder as extract.csv .

MBROPT(*REPLACE) replaces any file that is already in the MyFolder with the name extract.csv. It will also replace a file called EXTRACT.CSV or ExTrAcT.cSv too.

The STMFCCSSID is how the characters will be converted from EBCDIC to ASCII. In my experience I have found the best format is *STDASCII.

Finally we have to give what character is going to delimit the end of record. I always choose *CRLF, carriage return and line feed.

When this has completed you can copy the file extract.csv from the folder MyFolder to your PC and open it to make sure the data transferred is now in a PC readable form.

To zip the file I use the Java Jar command, which is run in the QSHELL environment using the STRQSH command.

STRQSH CMD('Jar cfM MyFolder/extract.zip + MyFolder/extract.csv')

The format of the Jar command is as follows: Jar  options  zipped-file-name  file-to-be-zipped

Each letter in the options is for something. There can be one or many options depending on what you want to do. Notice that the options are both upper and lower case. It is important to use the correct character as c does not do the same as C.

Option	Description
c	Create new archive (zip file)
C	Change to the specified directory and include following file
f	Specify archive file name
i	Generate index for specified Jar file
m	Include manifest information in manifest file
M	Do not create manifest file
t	List table of contents for archive
u	Update existing archive
v	Generate verbose ouput on standard output
x	Extract named file or all files from archive
0 (zero)	Store only, no zipping

In my example I used the options cfM, which translates to:

• I want to create a new archive file (c)
• I am specifying the zip file name (f)
• I do not want a manifest file (M)

You can see if the Jar was success by looking at the job's joblog. If you see the following then you know it was successful.

1200 - STRQSH CMD('Jar cfM MyFolder/extract.zip MyFolder/extract.csv') Command ended normally with exit status 0.

Having zipped the file, how do I unzip it and put it back into a DDS file?

First I have to extract the file from the zip file.

STRQSH CMD('Jar xf MyFolder/extract.zip + MyFolder/extract.csv')

I use the Jar command again this time with the options xf, which means:

• I want to extract the named file from the zip file (x)
• I need to specify the zip file name (f)

To copy the data from the IFS back into a DDS file I use the Copy From Import File, CPYFRMIMPF, which does the opposite of its sister command CPYTOIMPF.

CPYFRMIMPF FROMSTMF('MyFolder/extract.csv') + TOFILE(MYLIB/EXTRACT) + MBROPT(*REPLACE) + RCDDLM(*CRLF) + RPLNULLVAL(*FLDDFT)

The only different parameter is the RPLNULLVAL which replaces any null values with the default for the field type in the DDS file.

When this command has completed the data has been writen back to the DDS file.

I can put all of this together in a CL program, see below.

01 PGM 02 CPYTOIMPF FROMFILE(MYLIB/EXTRACT) + 03 TOSTMF('MyFOlder/extract.csv') + 04 MBROPT(*REPLACE) STMFCCSID(*STDASCII) + 05 RCDDLM(*CRLF) 06 STRQSH CMD('Jar cfM MyFolder/extract.zip + 07 MyFolder/extract.csv') 08 DEL OBJLNK('MyFolder/extract.csv') 09 STRQSH CMD('Jar xf MyFolder/extract.zip + 10 MyFolder/extract.csv') 11 CPYFRMIMPF FROMSTMF('MyFolder/extract.csv') + 12 TOFILE(MYLIB/EXTRACT) MBROPT(*REPLACE) + 13 RCDDLM(*CRLF) RPLNULLVAL(*FLDDFT) 14 ENDPGM

Line 2 copies the data from the DDS file to the CSV file in the IFS folder.

Line 6 zips it.

Line 8 deletes the CSV file in the IFS folder.

Line 9 unzips the file.

Line 11 copies it back into the DDS file.

You can learn more about these commands on the IBM website:

• CPYTOIMPF
• STRQSH
• CPYFRMIMPF

 

This article was written for IBM i 7.1, and it should work with earlier releases too.