Functions - io

createReadableChannel

Creates an in-memory channel, which will be a reference stream of bytes.

openReadableCsvFile

Retrieves a readable CSV channel from a given file path.

openReadableFile

Retrieves a ReadableByteChannel from a given file path.

openWritableCsvFile

Retrieves a writable CSV channel from a given file path.

openWritableFile

Retrieves a WritableByteChannel from a given file path.

print

Prints any or error value(s) to the STDOUT.

println

Prints any or error value(s) to the STDOUT followed by a new line.

readln

Retrieves the input read from the STDIN.

sprintf

Returns a formatted string using the specified format string and arguments.

createReadableChannel

(byte[] content)

returns ReadableByteChannel | Error

Creates an in-memory channel, which will be a reference stream of bytes.

 var byteChannel = io:createReadableChannel(content);

Parameters

  • content byte[]
  • Content, which should be exposed as a channel

  • Return Type

    (ReadableByteChannel | Error)
  • The ByteChannel representation to read the memory content or else an io:Error if any error occurred

openReadableCsvFile

(string path, Separator fieldSeparator, string charset, int skipHeaders)

returns ReadableCSVChannel | Error

Retrieves a readable CSV channel from a given file path.

 io:ReadableCSVChannel rCsvChannel = check io:openReadableCsvFile(srcFileName);

Parameters

  • path string
  • File path, which describes the location of the CSV

  • fieldSeparator Separator (default ,)
  • CSV record separator (i.e., comma or tab)

  • charset string (default UTF-8)
  • Representation of the encoding characters in the file

  • skipHeaders int (default 0)
  • Number of headers, which should be skipped

  • Return Type

    (ReadableCSVChannel | Error)
  • The ReadableCSVChannel, which could be used to iterate through the CSV records or else an io:Error if any error occurred.

openReadableFile

(string path)

returns ReadableByteChannel | Error

Retrieves a ReadableByteChannel from a given file path.

 io:ReadableByteChannel readableFieldResult = check io:openReadableFile("./files/sample.txt");

Parameters

  • path string
  • Relative/absolute path string to locate the file

  • Return Type

    (ReadableByteChannel | Error)
  • The ByteChannel representation of the file resource or else an io:Error if any error occurred

openWritableCsvFile

(string path, Separator fieldSeparator, string charset, int skipHeaders)

returns WritableCSVChannel | Error

Retrieves a writable CSV channel from a given file path.

 io:WritableCSVChannel wCsvChannel = check io:openWritableCsvFile(srcFileName);

Parameters

  • path string
  • File path, which describes the location of the CSV

  • fieldSeparator Separator (default ,)
  • CSV record separator (i.e., comma or tab)

  • charset string (default UTF-8)
  • Representation of the encoding characters in the file

  • skipHeaders int (default 0)
  • Number of headers, which should be skipped

  • Return Type

    (WritableCSVChannel | Error)
  • The WritableCSVChannel, which could be used to write the CSV records or else an io:Error if any error occurred

openWritableFile

(string path, boolean append)

returns WritableByteChannel | Error

Retrieves a WritableByteChannel from a given file path.

 io:WritableByteChannel writableFileResult = check io:openWritableFile("./files/sampleResponse.txt");

Parameters

  • path string
  • Relative/absolute path string to locate the file

  • append boolean (default false)
  • Whether to append to the end of file

  • Return Type

    (WritableByteChannel | Error)
  • The ByteChannel representation of the file resource or else an io:Error if any error occurred

print

(any | error... values)

Prints any or error value(s) to the STDOUT.

io:print("Start processing the CSV file from ", srcFileName);

Parameters

  • values any | error...
  • The value(s) to be printed.

println

(any | error... values)

Prints any or error value(s) to the STDOUT followed by a new line.

io:println("Start processing the CSV file from ", srcFileName);

Parameters

  • values any | error...
  • The value(s) to be printed.

readln

(any a)

returns string

Retrieves the input read from the STDIN.

 string choice = io:readln("Enter choice 1 - 5: ");

Parameters

  • a any
  • Any value to be printed

  • Return Type

    (string)
  • Input read from the STDIN

sprintf

(string format, any | error... args)

returns string

Returns a formatted string using the specified format string and arguments. Following format specifiers are allowed.

b - boolean

B - boolean (ALL_CAPS)

d - int

f - float

x - hex

X - HEX (ALL_CAPS)

s - string (This specifier is applicable for any of the supported types in Ballerina. These values will be converted to their string representation.)

 string s8 = io:sprintf("%s scored %d for %s and has an average of %.2f.", name, marks, subjects[0], average);

Parameters

  • format string
  • A format string

  • args any | error...
  • Arguments referred by the format specifiers in the format string

  • Return Type

    (string)
  • The formatted string