fileRead

 

 

Overview

The fileRead function reads data from a file {fileID} into the specified ByteVector Object {bytevector}. The ByteVector Object is always returned. If no ByteVector Object is specified, one will be created to hold the data that is read from the file.

Data is entered into a file with the fileWrite, fwriteln, or fdisplay functions, however, records are not actually committed to the file until the file is closed. Thus, attempting to read a record immediately after a fileWrite or fdisplay will result in an error. In order to verify records that have been written, it is necessary to close the file and save the file (fileClose with an option argument equal to 1) . The file can then be re-opened and read with the fileRead function.

Usage

The fileRead function is used to read data from an existing file (One that have been previously closed and saved file. See the fileClose function with an option argument equal to 1).

 

Syntax

Expression:

(fileRead fileID offset length bytevector)

(fileRead fileID pointer length)

(fileRead fileID length)

Arguments Name Type Description
Argument:fileID Integer An Integer representing the fileID of the file returned from a previous fileOpen function.
Argument:offsetInteger Optional. The integer index into the specified ByteVector where the data stream is to start . If no offset is specified, the offset defaults to zero.
Argument:length Integer Optional. The integer length of data which is to be read into the specified ByteVector. If no length is specified, the length defaults to the length to the end of the file.
Argument:bytevector ByteVector Optional. The ByteVector into which the data is to be placed. If no ByteVector is specified, one will be created.
Argument:pointer ByteVector Optional. The pointer where the data is to be placed.

Returns:

The ByteVector resulting from the file read is always returned as the value of this function.


 

Examples

Here are a number of links to Lambda coding examples which contain this instruction in various use cases.

 

Argument Types

Here are the links to the data types of the function arguments.

ByteVector Text Integer Boolean

Here are also a number of links to functions having arguments with any of these data types.

++ += + /=
/ * -- -=
- abortTransaction addMethod addi
appendWriteln avg badd balance
bcompareEQ bcompareGE bcompareGT bcompareLE
bcompareLT bcompareNE bdiv beginTransaction
binaryInsert binaryNand binaryNor binaryNot
binaryNxor binarySearch bitwiseAnd bitwiseNand
bitwiseNor bitwiseNot bitwiseNxor bitwiseOr
bitwiseShiftLeft bitwiseShiftRight bitwiseXor bmod
bmul boolean cadd ccompareEQ
ccompareGE ccompareGT ccompareLE ccompareLT
ccompareNE cdiv char character
checkPointTransaction clean clear cmod
cmul code commitTransaction compareEQ
compareGE compareGT compareLE compareLT
compareNE compare comparison compile
compress cons count csub
day days360 debugDetective debug
decode deleteRows delete dimension
disassemble display divi downcase
encode evalInSyncLocalContext exit exportCsv
exportSbf exportTab fact fdisplay
fileClose fileCopy fileDir fileDisplay
fileEraseDir fileErase fileExists fileMakeDir
fileOpen fileReadAll fileReadRecord fileRead
fileResize fileSeek fileSizeOf fileWriteAll
fileWrite filewriteln findBlock find
floor fraction freeBlock gc
gcd getRecursionCount hashString hour
iadd icompareEQ icompareGE icompareGT
icompareLE icompareLT icompareNE idiv
imod importCsv importSbf importTab
imul insertRows insert inside
inspect integer isAtom isBitVector
isBoolean isBound isByteVector isCharAlphabetic
isCharAlphanumeric isCharLowercase isCharName isCharNumeric
isCharUppercase isCharWhitespace isChar isCharacter
isComplex isDate isDictionary isDirectory
isEqual isError isEven isExact
isFloatVector isIdentical isImmediate isInexact
isInside isIntegerVector isInteger isLambda
isMatrix isMember isMoney isNegative
isNull isNumberMatrix isNumberVector isNumber
isObjectVector isObject isOdd isPair
isPcodeVector isPositive isString isStructure
isSymbol isText isTransaction isType
isVector isZero isub kurtosis
lcm left length lisp
list loadModule loadObject loadWorkspace
logConsole macroReplace makeQuotedList makeQuotedSymbol
max median member mid
min minute mod modi
money month morph muli
ncompareEQ ncompareGE ncompareGT ncompareLE
ncompareLT ncompareNE new number
objectToMatrix objectToNumMatrix objectToNumVector offset
onError pair parent parse
pointer preAllocateFixedMemoryBlocks product qt
quit random randomize range
rank refAttributes refValues ref
remove rename replace rept
reset resize right round
run saveModule saveObject saveRepository
saveWorkspace second setAttributes setBlock
setCar setCdr setLastCdr set
setf setq sizeof skew
sort sql sqrt srandom
stdev stdevp stringCiEQ stringCiGE
stringCiGT stringCiLE stringCiLT stringCiNE
stringFill stringToBVector stringToVector string
subi substitute substringCiEQ substringCiGE
substringCiGT substringCiLE substringCiLT substringCiNE
substringEQ substringFill substringGE substringGT
substringLE substringLT substringNE substring
sum sumsqr svmRegression symbolToTypeCode
symbol systemCheck system text
time trim type uncompress
uniqueInsert upcase var varp
vectorBinaryInnerProduct vectorBipolarInnerProduct vectorCosineInnerProduct vectorCubeInnerProduct
vectorDelete vectorExpInnerProduct vectorFill vectorInnerProduct
vectorLogInnerProduct vectorQuartInnerProduct vectorQuintInnerProduct vectorSigmoidInnerProduct
vectorSineInnerProduct vectorSquareInnerProduct vectorTanInnerProduct vectorTanhInnerProduct
version writelg writeln year

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