Using KSAM XL and KSAM 64 > Chapter 3 Obtaining File Information

Accessing User-Defined Labels

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A user label is an optional method of adding documentation to your file. You can write your own labels to a KSAM file with the FWRITELABEL intrinsic. For example, you can use a label to enter the date and time of the last file update. These labels are read with the FREADLABEL intrinsic.

Specify the number of user labels to be created in the userlabel parameter of the FOPEN intrinsic. In order to write labels, the file must be open. To do so, set the aoptions parameter of the FOPEN intrinsic to one of the write, input/output, or update access specifications.

The following example shows the intrinsic call to write information to the second file label.


  FWRITELABEL(KFILNUM,LABELBUF,60,1);

In this example, the 60 halfwords of text contained in the variable LABELBUF are to be written in the second user label. Note that label numbering starts with zero. The second label is identified by the number 1 in the last parameter. If this parameter contains zero or is omitted, the first label is written.

You can read the contents of user labels using the FREADLABEL intrinsic. During the normal reading of a file, user labels are skipped. The FREADLABEL intrinsic, therefore, should be called immediately after the file has been opened. To read a user label, the file must be opened with read, input/output, or update access, and the user labels to be read must be identified.

Issue the following FREADLABEL intrinsic call to read the user label written in the previous example.


  FREADLABEL(KFILNUM,LABEL2,,1);

The variable LABEL2 returns the contents of the second user label. By default, the call returns 128 halfwords from the label.

Accessing Key Information From a Program

Chapter 4 Opening and Closing the File

Accessing User-Defined Labels

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