| Routine ID: Z310 | |
|---|---|
| Author(s): J. Zoll | Library: KERNLIB, UNIX and VMS |
| Submitter: | Submitted: 19.09.1991 |
| Language: Fortran + C | Revised: |
The routines of this package are an interface to the C library functions open, read, write, lseek, close, to permit a Fortran program to handle an unstructured Unix file as a string of fixed-length binary records. Both sequential and direct-access READ / WRITE can be simulated.
These routines are simple little interface routines, there is no book-keeping done of the files which have been opened, the properties of the file have to be specified on each call, and the user is responsible for the consistency of all his calls for a particular file.
Processing has to be different for a disk file or for a tape file; therefore the medium must be indicated in the calls. Also, a user could take the source of these routines and modify them to add other branches for special processing.
New files are opened with the default permissions 644; one may set different permissions by calling CFPERM just before calling CFOPEN, which resets to the default after every call.
Three parameters are common to almost all routines :
LUNDES is the file-descriptor of C to identify the file;
with CFOPEN this is an output parameter,
for all other routines it is an input parameter.
MEDIUM = 0 for disk file, normal
1 tape file, normal
2 disk file, user coded I/O
3 tape file, user coded I/O
NWREC is the number of machine words for each one
of the fixed-length records.
In the examples below it is assumed that for a given file these
three parameters are available in something like COMMON storage.
Structure:
SUBROUTINE subprograms
User Entry Names:
CFOPEN, CFGET, CFPUT,
CFSIZE, CFTELL, CFSEEK, CFREW,
CFCLOS, CFPERM
Files Referenced: Parameter
Usage:
Note: the symbol * designates output parameters.
Open a file
CALL CFOPEN(LUNDES,MEDIUM,NWREC, CHMODE, NBUF, CHNAME, ISTAT)
LUNDES* file-descriptor returned
CHMODE CHARACTER string selecting the IO mode :
= 'r' open for reading
'r+' open for read/write
'w' create or truncate for writing
'w+' open for write/read, create or truncate
'a' append
'a+' open for append/read
[ add the letter "l" if labeled tape,
action on this is not yet implemented ]
NBUF not used for the time being, always give zero
CHNAME name of the file, CHARACTER variable
ISTAT* status, =zero if success
For example, create a new file in the current directory :
MEDIUM = 0
NWREC = 900
CALL CFOPEN(LUNDES,MEDIUM,NWREC, 'w', 0, 'run201.dat', ISTAT)
IF(ISTAT .NE. 0) GO TO trouble
Read next record
CALL CFGET(LUNDES,MEDIUM,NWREC, NWTAK, MBUF, ISTAT)
*NWTAK* input: number of words to be read
output: number of words actually read
MBUF* vector to be read into
ISTAT* status, = zero if success,
= -1 if end-of-file
To simulate direct-access reading one has to call CFSEEK first.
For example:
<< if the 7th record of the file is to be read:
CALL CFSEEK(LUNDES,MEDIUM,NWREC, 6, ISTAT)
IF(ISTAT .NE. 0) GO TO trouble >>
NWTAK = NWREC
CALL CFGET(LUNDES,MEDIUM,NWREC, NWTAK, MBUF, ISTAT)
IF(ISTAT .EQ.-1) GO TO eof
IF(ISTAT .NE. 0) GO TO trouble
Write next record
CALL CFPUT(LUNDES,MEDIUM,NWREC, MBUF, ISTAT)
MBUF vector to be written, NWREC words
ISTAT* status, =zero if success
Get the size of the file
CALL CFSIZE(LUNDES,MEDIUM,NWREC, NRECT, ISTAT)
NRECT* number of records on the file
ISTAT* status, =zero if success
Careful : this will position the file to the end.
Get the current file position
CALL CFTELL(LUNDES,MEDIUM,NWREC, NRECC, ISTAT)
NRECC* number of records before current
ISTAT* status, =zero if success
Set the current file position
CALL CFSEEK(LUNDES,MEDIUM,NWREC, NRECC, ISTAT)
NRECC number of records before current
ISTAT* status, =zero if success
For example :
CALL CFSEEK(..., 0, ISTAT) position to start-of-file
CALL CFSEEK(..., 6, ISTAT) position to 7th record
use CFSIZE to position to end-of-file
Rewind the file
CALL CFREW(LUNDES,MEDIUM)
Close the file
CALL CFCLOS(LUNDES,MEDIUM)
Set the permissions for the next open
CALL CFPERM(IPERM)
IPERM the permissions as a decimal integer,
as returned by STATF (Z265) for example
For example (using NCOCTI of M432) :
CALL CFPERM(NCOCTI('660'))
set read and write for owner and group only.