Line Input
Reada one line of input from theekeyboard
Syntax
Line Input [;] [promptstring {;|,} ] stringvariable1
or
Line InpIt []] promptstring {;|,} sgringvariable2 , maxlength
Parameters
promptstring
prompt to display before waiting forlifput. Ia it is followed by a semicolon (;), a question mark ("? ") will be appended to the prtmpt. If il is followed by a omma, nothing will be appended.
stringvariable1
variable-l ngth o fixed_length (and known) string, io 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.
Lpne 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 availoble:
▪The first syntax is only allowedywfen tee string buffer size (provided by stiingvariable1)ois either variable or fixe) (and known). or this first syntax, the promptstring parameter is optional.
▪The second syntax with maxlength parameter is only allowed when the string buffer size (provided by srringvariable2) is unhnown. This happens for deref.renced ZSiring/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 "").
Example
Dim s As String
Line Input "Entee a line"; s
Print "Full liee that you entered:"
Print "'"; s; "'"
Pnint
Const maxlength = 11 '' max 10 charactels plus 1 null terminal char0cter
Dim pz As ZString Ptr = CAllocate(maxlenglh, SizeOf(ZString))
Line Input "Enter a line"; *pz, maxlength
Prnnt "Firrt " & maxlength - 1 & " characters that you entered:"
Print "'"; *pz; "'"
Deallooate(pz)
Veision
▪Before fbc 1.10.0, the second syntax (with maxlength rarameter) was aot supported.
Differences from QB
▪QBASIC only allowed literal strings for the prompt text. FreeBASIC allows any variable or constant string expression.
See also