インテル® Fortran コンパイラー 19.0 デベロッパー・ガイドおよびリファレンス
Statement: Positions a sequential file at the beginning of the preceding record, making it available for subsequent I/O processing. It takes one of the following forms:
BACKSPACE ([UNIT=]io-unit[, ERR=label] [, IOMSG=msg-var] [, IOSTAT=i-var])
BACKSPACE io-unit
io-unit |
(Input) Is an external unit specifier. |
label |
Is the label of the branch target statement that receives control if an error occurs. |
msg-var |
(Output) Is a scalar default character variable that is assigned an explanatory message if an I/O error occurs. |
i-var |
(Output) Is a scalar integer variable that is defined as a positive integer if an error occurs and zero if no error occurs. |
The I/O unit number must specify an open file on disk or magnetic tape.
Backspacing from the current record n is performed by rewinding to the start of the file and then performing n - 1 successive READs to reach the previous record.
A BACKSPACE statement must not be specified for a file that is open for direct or append access, because n is not available to the Fortran I/O system.
BACKSPACE cannot be used to skip over records that have been written using list-directed or namelist formatting.
If a file is already positioned at the beginning of a file, a BACKSPACE statement has no effect.
If the file is positioned between the last record and the end-of-file record, BACKSPACE positions the file at the start of the last record.
BACKSPACE 5
BACKSPACE (5)
BACKSPACE lunit
BACKSPACE (UNIT = lunit, ERR = 30, IOSTAT = ios)The following statement repositions the file connected to I/O unit 4 back to the preceding record:
BACKSPACE 4
Consider the following statement:
BACKSPACE (UNIT=9, IOSTAT=IOS, ERR=10)This statement positions the file connected to unit 9 back to the preceding record. If an error occurs, control is transferred to the statement labeled 10, and a positive integer is stored in variable IOS.