XL Fortran for AIX 8.1

Language Reference



The BACKSPACE statement positions an external file, connected for sequential access, before the preceding record.



is an external unit identifier. The value of u must not be an asterisk or a Hollerith constant.

is a list that must contain one unit specifier ([UNIT=]u) and can also contain one of each of the other valid specifiers:

[UNIT=] u
is a unit specifier in which u must be an external unit identifier whose value is not an asterisk. An external unit identifier refers to an external file that is represented by a scalar integer expression, whose value is in the range 1 through 2147483647. If the optional characters UNIT= are omitted, u must be the first item in position_list.

is an input/output status specifier that specifies the status of the input/output operation. ios is a scalar variable of type INTEGER(4) or default integer. When the BACKSPACE statement finishes executing, ios is defined with:

ERR= stmt_label
is an error specifier that specifies the statement label of an executable statement in the same scoping unit to which control is to transfer in the case of an error. Coding the ERR= specifier suppresses error messages.


If there is no preceding record, the file position does not change. If the preceding record is the endfile record, the file is positioned before the endfile record. You cannot backspace over records that were written using list-directed or namelist formatting.

If the ERR= and IOSTAT= specifiers are set and an error is encountered, transfer is made to the statement specified by the ERR= specifier and a positive integer value is assigned to ios.

+-------------------------------IBM Extension--------------------------------+

If IOSTAT= and ERR= are not specified,

+----------------------------End of IBM Extension----------------------------+


99 PRINT *, "Unable to backspace file." END

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