MPE/iX Intrinsics Reference Manual (32650-90905)

Chapter 6 263
Command Definitions (FLUSHLOG-GETUSERMODE)
FREADLABEL
FREADLABEL
NM and CM callable.
Reads a user-defined label from a disk or magnetic tape file.
Syntax
I16V UDS I16V I16V
FREADLABEL(
filenum,buffer , length,labelid );
Parameters
filenum 16-bit signed integer by value (required)
Passes the file number of the file whose label is to be read.
buffer user-defined structure (required)
Returns the label that was read. This structure must be large enough to
hold the number of half words specified by
length .
length 16-bit signed integer by value (optional)
Passes the number of half words to be transferred from the label, <=128.
Default: 128 half words
labelid 16-bit signed integer by value (optional)
Passes the label number. For labeled tapes,
labelid is ignored. The next
sequential label is read.
Default: Zero
Operation Notes
When a disk file is opened, user labels can be read from, or written to, in any order, at any
time, regardless of access capabilities to the rest of the file. A disk file can have <=254
128-half word user-defined labels.
A magnetic tape file (if labeled) must be labeled with an ANSI-standard or IBM-standard
label. The operating system automatically skips over any unread user-defined labels when
the first FREAD intrinsic call for files is issued. To read a user-defined label, you should call
the FREADLABEL intrinsic immediately after an FOPEN/HPFOPEN intrinsic has opened the
file. The user-defined label must be 40 half words in length to conform to the length of the
ANSI-standard or IBM-standard label.
Condition Codes
CCE (2) Request granted. The label was read.
CCG (0) Request denied. A label was referenced beyond the label written on the
file.