FREADLABEL
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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. |
| CCL (1) | Request denied. The label was not read; an error occurred. |
Related Information
| Intrinsics | FREAD, FREADBACKWARD, FREADBYKEY, FREADC, FREADDIR, FREADSEEK, FWRITELABEL |
| Manuals | Accessing Files Programmer's Guide |
|
FREADDIR |
FREADSEEK |