VMS Help READ  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Reads a single record from a specified input file and assigns the
    record's contents to a specified symbol name.

    Format

      READ  logical-name[:] symbol-name

1 - Parameters

 logical-name[:]

    Specifies the logical name of the input file from which a record
    is to be read. Use the logical name assigned by the OPEN command
    when the file was opened. (The OPEN command assigns a logical
    name to a file and places the name in the process logical name
    table.)

    In addition, you can specify the process-permanent files
    identified by the logical names SYS$INPUT, SYS$OUTPUT, SYS$ERROR,
    and SYS$COMMAND.

 symbol-name

    Specifies the name of a symbol to be equated to the contents of
    the record. The name must be 1 to 255 alphanumeric characters and
    must start with an alphabetic letter, an underscore (_),  or a
    dollar sign ($).

    When you specify a symbol name for the READ command, the command
    interpreter places the symbol name in the local symbol table
    for the current command level. If the symbol has already been
    defined, the READ command redefines it to the new value being
    read.

2 - Qualifiers

 2.1 - /DELETE

    Deletes a record from an indexed file after it has been read. An
    indexed file must be opened with the /READ and /WRITE qualifiers
    in order to use the READ/DELETE command.

 2.2 - /END_OF_FILE

       /END_OF_FILE=label

    Transfers control to the location specified by the label keyword
    (in the current command procedure) when the end of the file is
    reached. When the last record in the file is read, the OpenVMS
    Record Management Services (RMS) returns an error condition
    indicating the end-of-file (EOF). If the /END_OF_FILE qualifier
    is specified, the command interpreter transfers control to the
    command line at the specified label.

    If the /END_OF_FILE qualifier is not specified, control is given
    to the error label specified with the /ERROR qualifier when the
    end of the file is reached. If neither the /ERROR nor the /END_
    OF_FILE qualifier is specified, then the current ON condition
    action is taken.

 2.3 - /ERROR

       /ERROR=label

    Transfers control to the location specified by the label keyword
    (in the current command procedure) when a read error occurs.
    If no error routine is specified and an error occurs during the
    reading of the file, the current ON condition action is taken.

    Overrides any ON condition action specified.

    If an error occurs and the target label is successfully given
    control, the reserved global symbol $STATUS retains the error
    code.

 2.4 - /INDEX

       /INDEX=n

    Specifies the index (n) to be used to look up keys when reading
    an indexed file.

    If you do not specify the /INDEX qualifier, the most recent
    /INDEX qualifier value is used. If a previous value was not
    specified, the primary index is used (/INDEX=0).

 2.5 - /KEY

       /KEY=string

    Reads a record with the key that matches the specified character
    string. Binary and integer keys are not allowed. This qualifier,
    when used together with the /INDEX qualifier, allows you random
    access to indexed files.

    Key matches are made by comparing the characters in the /KEY
    string to characters in the record key.

    To read records at random in an indexed file, you must specify
    the /KEY qualifier. Once a record is read randomly, all
    subsequent reads without the /KEY qualifier access records in
    the indexed file sequentially.

 2.6 - /MATCH

       /MATCH=option

    Specifies the key match algorithm to be used when searching for
    matching keys. Specify one of the following options:

    EQ      Selects keys equal to the match value (default).
    GE      Selects keys greater than or equal to the match value.
    GT      Selects keys greater than the specified key.

    If you are reading indexed files and you do not use the /MATCH
    qualifier, the default is /MATCH=EQ.

 2.7 - /NOLOCK

    Specifies that the record to be read not be locked and enables a
    record to be read that has been locked by other accessors.

    By default, records are locked as they are read and unlocked on
    the next I/O operation on the file.

 2.8 - /PROMPT

       /PROMPT=string

    Specifies an alternate prompt string to be displayed when reading
    from the terminal. The default prompt string is DATA:.

 2.9 - /TIME_OUT

       /TIME_OUT=n
       /NOTIME_OUT (default)

    Specifies the number of seconds after which the READ command is
    terminated if no input is received. If you enter the /TIME_OUT
    qualifier, you must specify a value from 0 to 255.

    If you enter both the /ERROR=label and /TIME_OUT qualifiers, and
    the time limit expires, the error branch is taken.

3 - Examples

    1.$ OPEN IN NAMES.DAT
      $ LOOP:
      $ READ/END_OF_FILE=ENDIT IN NAME
         .
         .
         .
      $ GOTO LOOP
      $ ENDIT:
      $ CLOSE IN

      The OPEN command opens the file NAMES.DAT for input and assigns
      it the logical name of IN. The READ command reads records from
      the file IN and places the contents into the symbol NAME. The
      READ command specifies the label ENDIT to receive control when
      the last record in the file has been read. The procedure loops
      until all records in the file have been processed.

    2.$ READ/ERROR=READERR/END_OF_FILE=OKAY  MSGFILE  CODE
         .
         .
         .
      $ READERR:
      $ CLOSE MSGFILE
         .
         .
         .
      $ OKAY:
      $ CLOSE MSGFILE
      $ EXIT

      The READ command reads records from the file MSGFILE and
      places the contents into the symbol CODE. The READ command
      also uses the /ERROR and /END_OF_FILE qualifiers to specify
      labels to receive control at the end-of-file (EOF) and on
      error conditions. At the EOF, control is transferred to the
      label OKAY. On other read errors, control is transferred to the
      READERR label.

    3.$ READ SYS$COMMAND  DATA_LINE
      $ WRITE  OUTPUT_FILE  DATA_LINE
         .
         .
         .

      The READ command requests data from the current SYS$COMMAND
      device. If the command procedure containing these lines is
      executed interactively, the command issues a prompt to the
      terminal, accepts a line of data, and equates the data entered
      to the symbol name DATA_LINE.

      Then the WRITE command writes the value of the symbol DATA_LINE
      to the file identified by the logical name OUTPUT_FILE.

    4.$ OPEN/READ INPUT_FILE TRNTO::INVENTORY.DAT
      $ OPEN/APPEND OUTPUT_FILE RECEIVE.DAT
      $ READ INPUT_FILE DATA_LINE
      $ WRITE OUTPUT_FILE DATA_LINE

      The OPEN/READ command opens the file INVENTORY.DAT at the
      remote node TRNTO for reading and assigns it the logical name
      INPUT_FILE. The OPEN/APPEND command opens the file RECEIVE.DAT
      in the current default directory. The READ command requests
      data from the file INVENTORY.DAT at the remote node TRNTO. The
      WRITE command writes the value of the symbol DATA_LINE to the
      end of the local file RECEIVE.DAT.