HP 3000 Manuals HP 3000 Manuals
FREADLABEL
NM and CM callable.
Reads a user-defined label from a disk or magnetic tape file.
Syntax
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| I16V UDS I16V I16V |
| FREADLABEL(filenum,buffer,length,labelid);|
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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.
CCL (1) Request denied. The label was not read; an error
occurred.
Related Information
Intrinsics None
Commands None
Manuals Accessing Files Programmer's Guide (32650-90017)