LINE INPUT

• Source: https://www.freebasic.net/wiki/wikka.php?wakka=KeyPgLineinput
• Last revised: 2022-04-30

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Reads one line of input from the keyboard

Syntax

Line Input [;] [promptstring {;|,} ] stringvariable1

or

Line Input [;] promptstring {;|,} stringvariable2 , maxlength

Parameters

promptstring

prompt to display before waiting for input. If it is followed by a semicolon (;), a question mark ("? ") will be appended to the prompt. If it is followed by a comma, nothing will be appended.

stringvariable1

variable-length or fixed_length (and known) string, to receive the line of text

stringvariable2

dereferenced {z|w}string pointer or {z|w}string variable passed by reference (string buffer size unknown for both), to receive the line of text

maxlength

maximum number of characters allowed to be written to the string buffer, including the NULL terminator

Description

Reads a line of text from the keyboard and stores it in a string variable.

The promptstring - if any - is written to the screen at the current cursor location, and characters read are echoed to the screen immediately following the prompt. If no prompt is specified, characters are echoed at the current cursor location.

The optional leading semicolon (;) after Line Input is similar to the optional trailing semicolon in a Print statement: the cursor will remain on the same line after all of the characters have been echoed, otherwise, the cursor will move to the beginning of the next line.

Line Input has a limited edit capacity: it allows to use the left and right cursor keys to navigate the text, and to erase or insert characters. If a better user interface is needed, a custom input routine should be used.

Two syntaxes are available:

• The first syntax is only allowed when the string buffer size (provided by stringvariable1) is either variable or fixed (and known). For this first syntax, the promptstring parameter is optional.
• The second syntax with maxlength parameter is only allowed when the string buffer size (provided by stringvariable2) is unknown. This happens for dereferenced Zstring/Wstring pointers, or Zstring/Wstring variables passed by reference. This can used to truncate the text line to be read, or avoid overflowing beyond allocated data of the provided string buffer. For this second syntax, the promptstring parameter is mandatory even if it is empty (use "").

Examples

start GeSHi

Dim s As String
Line Input "Enter a line"; s
Print "Full line that you entered:"
Print "'"; s; "'"
Print

Const maxlength = 11  '' max 10 characters plus 1 null terminal character
Dim pz As ZString Ptr = CAllocate(maxlength, SizeOf(ZString))
Line Input "Enter a line"; *pz, maxlength
Print "First " & maxlength - 1 & " characters that you entered:"
Print "'"; *pz; "'"
Deallocate(pz)

end GeSHi

Version

• Before fbc 1.10.0, the second syntax (with maxlength parameter) was not supported.

Differences from QB

• QBASIC only allowed literal strings for the prompt text. FreeBASIC allows any variable or constant string expression.

See also

• Line Input #
• Input

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