TOPS-20 Commands Reference Manual

SKIP

Moves a magnetic tape set forward over a specified number of files or records, or to the logical end of the tape set.

Format

@SKIP (DEVICE) dev:  n units

where:

Restrictions

SKIP With Open Files

If you have given a CTRL/C to exit from a program that has opened a file in a magnetic tape set and you then give the SKIP command for that tape set, the system will first ask if you want to close the associated file. You must do so for SKIP to succeed, but you will probably be unable to continue the program from that point because the file will now be closed.

RECORDS Argument Used for Unlabeled Tapes Only

You cannot use the RECORDS argument to the SKIP command when using a labeled tape, because read and write operations for labeled tapes always move the tape to the beginning of a file.

Warning

Skipping Past LEOT (Unlabeled Tapes Only)

If you specify too large a value for n in the SKIP command line, you can move past the logical end of tape (LEOT). In this case, the operator may have to intervene before your tape control commands will have effect again. You must be sure how many files you have in the tape set if you use SKIP n rather than SKIP LEOT. This problem can occur for any tapes mounted on drives of the form MTAn:, or for unlabeled tapes mounted on drives of the form MTn:.

Related Commands

dev:	is the name of the tape set or magnetic tape drive that you want to move forward.
n	is the number of files or records over which you want to skip. The colon after the device name is optional.
units	is either FILES or RECORDS, where records are sections of a file; or LEOT, to skip to the logical end of the tape set, which is the next point on the tape set having two adjacent EOF (end-of-file) marks. Default units - FILES

BACKSPACE	for moving a magnetic tape backward a specified number of files or records
REWIND	for returning a magnetic tape to its load point
UNLOAD	for rewinding a magnetic tape completely onto the source reel (only for tapes mounted on drives having device names of the form MTAn:)

Examples

Skip over the next 2 files on the magnetic tape you are using (mounted on magnetic tape drive MT0: in this case).
```
@SKIP MT0: 2 FILES
```
Skip over the next two records on an unlabeled tape.
```
@SKIP MTA0: 2 RECORDS
```

Use the MOUNT command to ask the operator to mount your tape in write-enabled mode, then copy 3 files to the tape from your directory on structure SNARK:. Use the REWIND command to go back to the beginning, and the SKIP command to skip over the first file. Use the COPY command to have the next file (FIL-2) printed on your terminal, then give the SKIP command again to skip to the logical end-of-tape. You are skipping only one file, FIL-3, in this case.

@MOUNT TAPE DAY:/WRITE-ENABLED
[Mount Request DAY Queued, Request-ID 187]
[Tape set DAY, Volume DAY mounted]
[DAY: defined as MT0:]
@REWIND DAY:
@MOUNT STRUCTURE SNARK:
Structure SNARK: mounted
@ACCESS SNARK:
@COPY SNARK:FIL-1.TAP DAY:
 SNARK:FIL-1.TAP.1 => MT0:FIL-1 [OK]
@COPY SNARK:FIL-2.TAP DAY:
 SNARK:FIL-2.TAP.1 => MT0:FIL-2 [OK]
@COPY SNARK:FIL-3.TAP DAY:
 SNARK:FIL-3.TAP.1 => MT0:FIL-3 [OK]
@REWIND DAY:
@SKIP DAY: 1
@COPY DAY: TTY:
 T0: => TTY:

!THIS IS THE SECOND FILE.!
@SKIP DAY:LEOT

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