READ

READ statement allows a program to read a record from a previously opened file into a variable.

COMMAND SYNTAX

    READ variable1 FROM {variable2,} expression { SETTING setvar }  \
         { ON ERROR statements } THEN | ELSE statements

SYNTAX ELEMENTS

variable1 is the identifier into which the record will be read.

variable2, if specified, should be a jBC variable that has previously been opened to a file using the OPEN statement. If variable2 is not specified then the default file is assumed.

The expression should evaluate to a valid record key for the file.

If the SETTING clause is specified and the reading process fails, setvar will be set to one of the following values:

INCREMENTAL FILE ERRORS

CodeDescription
128No such file or directory
4096Network error
24576Permission denied
32768Physical I/O error or unknown error

If ON ERROR is specified, the statements following the ON ERROR clause will be executed for any of the above Incremental File Errors except error 128.

NOTES

If you wish to set a lock on a record, you should do so explicitly with the READU statement.

EXAMPLE

       IF NOT( GETENV('TAFC_HOME', V.HOME) ) THEN
          CRT 'TAFC_HOME not defined'
          STOP
       END
       OPEN V.HOME : '/jbcmessages' TO F.MSG ELSE ABORT 201, 'jbcmessages'
       READ R.MSG FROM F.MSG, 'ARRAY_ILLEGAL_SIZE' ELSE
          CRT 'ERROR READING THE FILE, ID=ARRAY_ILLEGAL_SIZE'
          STOP
       END
       CRT R.MSG

Program output: 

     ∗∗ Error [ ARRAY_ILLEGAL_SIZE ] ∗∗ ^NEWLINE^^DEBUGQUIT^Attempt to DIMension
     a variable with 0 or fewer elements , Line ^LINENO^ , Source ^SOURCENAME^

Last update: Sat, 16 Jul 2022 15:34