Read and write text lines

When the channel is open, use the readLine()/writeLine() methods to read and write simple text lines of data terminated by a line terminator.

When using the readLine() and writeLine() functions, a LF character represents the end of a line.

For example, a simple text file can look like this:

first line
second line
third line

Sample code to read the above text file is as follows:

MAIN
  DEFINE i INTEGER
  DEFINE s STRING
  DEFINE ch base.Channel 
  LET ch = base.Channel.create()
  CALL ch.openFile("file.txt","r")
  LET i = 1
  WHILE TRUE
    LET s = ch.readLine()
    IF ch.isEof() THEN EXIT WHILE END IF
    DISPLAY i, " ", s 
    LET i = i + 1
  END WHILE
  CALL ch.close()
END MAIN

LF characters escaped by a backslash are not interpreted as part of the line during a readLine() call.

When a line is written, any LF characters in the string will be written as is to the output. When a line is read, the LF escaped by a backslash is not interpreted as part of the line.

For example, this code:

CALL ch.writeLine("aaa\\\nbbb")  -- [aaa<bs><lf>bbb]
CALL ch.writeLine("ccc\nddd")    -- [ccc<lf>ddd]

would generate this output:

aaa\
bbb 
ccc 
ddd

and the subsequent readLine() will read four different lines, where the first line is ended by a backslash:

Read 1 aaa<bs>
Read 2 bbb 
Read 3 ccc 
Read 4 ddd