Line Input #
Reads one line of text from a file
Line Input #file number, string_variable_1
file number
Reads a line from an open text file (opened for Input through a bound file number) and stores it in a string variable.
A line of text ends at, but does not include the end of line characters. An end of line character may be the LF character (Chr(10)) or the CRLF character pair (Chr(13,10)).
Two syntaxes are available:
Syntax
Line Input #file number, string_variable_1
or
Line Input #file number, string_variable_2 , max_lengthParameters
file number
file number of an file opened for Input
string_variable_1variable-length or fixed_length (and known) string, to receive the line of text
string_variable_2dereferenced {z|w}string pointer or {z|w}string variable passed by reference (string buffer size unknown for both), to receive the line of text
max_lengthmaximum number of characters allowed to be written to the string buffer, including the NULL terminator
Description
Reads a line from an open text file (opened for Input through a bound file number) and stores it in a string variable.
A line of text ends at, but does not include the end of line characters. An end of line character may be the LF character (Chr(10)) or the CRLF character pair (Chr(13,10)).
Two syntaxes are available:
- The first syntax is only allowed when the string buffer size (provided by string_variable_1) is either variable or fixed (and known).
- The second syntax with max_length parameter is only allowed when the string buffer size (provided by string_variable_2) 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.
- Using Line Input # is naturally dedicated to Input Access file mode.
- It is also allowed in Binary/Random Access file mode, but this was never well tested and results may vary.
- It is also allowed in Binary/Random Access file mode, but this was never well tested and results may vary.
Example
Open "myfile.txt" For Output As #1
Print #1, "Hello, World"
Close #1
Dim s As String
Open "myfile.txt" For Input As #1
Line Input #1, s
Close #1
Print "'" & s & "'"
Const maxlength = 6 '' max 5 characters plus 1 null terminal character
Dim pz As ZString Ptr = CAllocate(maxlength, SizeOf(ZString))
Open "myfile.txt" For Input As #1
Line Input #1, *pz, maxlength
Close #1
Print "'" & *pz & "'"
Deallocate(pz)
Print #1, "Hello, World"
Close #1
Dim s As String
Open "myfile.txt" For Input As #1
Line Input #1, s
Close #1
Print "'" & s & "'"
Const maxlength = 6 '' max 5 characters plus 1 null terminal character
Dim pz As ZString Ptr = CAllocate(maxlength, SizeOf(ZString))
Open "myfile.txt" For Input As #1
Line Input #1, *pz, maxlength
Close #1
Print "'" & *pz & "'"
Deallocate(pz)
Version
- Before fbc 1.10.0, the second syntax (with max_length parameter) was not supported.
Differences from QB
- None
See also