MAG TAPE UTILITY R. E. BURROUGHS 18-AUGUST-1980 CHAPTER 1 INTRODUCTION MGT is a PDP-11 program running under RSX to facilitate the reading and writing of ASCII mag tapes. It will allow the user to do the following: 1. Position mag tape 1. Rewind mag tape 2. Skip xxx records (plus or minus) 3. Skip xxx files (plus or minus) 4. Write an EOV mark at the end of a file 2. Write a mag tape 1. Disk to tape copy 2. Disk to tape blank fill 3. Disk to tape blocked (with or without a line terminator) 3. Read a mag tape 1. Tape to disk copy 2. Tape to disk and deblock INTRODUCTION PAGE 1-2 3. Tape to terminal or line printer 4. Tape to tape copy CHAPTER 2 GENERAL OPERATION MGT can be initiated in several ways >MGT >MGT command line >MGT @command file MGT uses the GCML MACRO with a nesting depth of 2. Therefore all rules re- garding indirect command files are applicable. Command line format OUTFILE/SW=INFILE Note that all switches are applied to the output file spec. The following is a summary of recognizable switches. /RW Rewind tape /SK:xxx Skip xxx records /SF:xxx Skip xxx files /EV Write EOV mark GENERAL OPERATION PAGE 2-2 /AL Copy all files (tape to tape only) /BF:xxx Blank fill records. xxx is record length /BL:xxx Block data to tape. xxx is record length /LT:xxx Use xxx as line terminator for deblocking xxx represents an octal number unless followed by a decimal point. Maximun record size is 4096.. CHAPTER 3 POSITIONING MAG TAPE MGT will allow the user to position a mag tape at a given record or file or at the BOT. Also, if the tape is at an EOF mark an EOV mark may be written. In the case of a /SF or /SK switch, plus or minus values are allowed. The following are some examples of the proper use of these switches. MGT>MT0:/RW Rewind MT0 MGT>MS0:/SK:4 Skip foreward 4 records on MS0 MGT>MT0:/SF:-6 Skip backward 6 files on MT0 MGT>MT0:/EV Write an EOF mark at the current position on MT0. This is an EOV mark if MT0 is positioned at an EOF mark. Note that there is not an input file spec. associated with these commands. CHAPTER 4 WRITING A MAG TAPE Files may be written to mag tape in three different ways. The first is just a straight copy from disk to tape. Records of less than 14 bytes will be padded with nulls. The second is blank filled records. Records will be filled with ASCII blanks. The third is blocked mode. Data will be packed into a buffer until it is filled and then written out to tape. If a line terminator is also given, it will be added to the end of each record read from disk before it is packed into the buffer. The following are some examples of the proper use of these switches when writting a tape. MGT>MT0:=TEST.DAT The file TEST.DAT will be copied to MT0. MGT>MS0:/BF:132.=TEST.DAT The file TEST.DAT will be written to MS0 with each record extended to 132. bytes and filled with ASCII blanks. MGT>MT0:/BL:2000.=TEST.DAT The file TEST.DAT will be written to MT0. Each record from TEST.DAT will be packed into a 2000. byte buffer. When the buffer is full it will be written to MT0. MGT>MT0:/BL:2000./LT:7=TEST.DAT This will accomplish the the same as above, except that the octal no. 7 will be added to the end of each record as it is packed into the output buffer. MGT>MT0:=TI: This will allow a user to write a a magtape from his terminal. Records are terminated by a carriage return and end of file is signaled by a control/z. CHAPTER 5 READING A MAG TAPE There are essintially two ways to read a mag tape. The first is just a straight copy from mag tape to disk and the second is to read the mag tape and deblock it using a given line terminator. Additionally the output device may be a teletype or a line printer if the user just wishes to see what is on the tape. The following are some examples of reading a mag tape. MGT>TEST.DAT=MT0: The file at the current position of MT0 is copied to the disk file TEST.DAT. MGT>TEST.DAT/LT:7=MS0: The file at the current position of MS0 will be copied to the disk file TEST. DAT. The octal value 7 will be used as an end of record mark and will not appear on the disk file. MGT>TEST.DAT/BL:80.=MT0:This is the same as above except that the file will be deblocked with record lengths of 80. Care should be used in determining the blocking factor. It must be a multiple of the input record length or else some data will be lost. MGT>LP:=MT0: The file at the current position of MT0 will be copied to the line printer. CHAPTER 6 TAPE TO TAPE COPY MGT will also allow the user to copy a tape to a tape. This is done one file at a time unless the /AL switch is added. Then the tape copying will pro- cede until an EOV mark is encountered. MGT>MT0:=MS0: The file at the current position of MS0 will be copied to current position of MT0. MGT>MT0:/AL=MT1: All the files on MT1 will be copied to MT0 untill an EOV mark is encountered.