The BACKSPACE statement positions the specified file to just before the preceding record.
BACKSPACE u
BACKSPACE ([UNIT= ] u [, IOSTAT=ios ] [, ERR=s ])
Parameter |
Description |
u |
Unit identifier of the external unit connected to the file |
ios |
I/O status specifier, integer variable, or an integer array element |
s |
Error specifier: s must be the label of an executable statement in the same program unit in which the BACKSPACE statement occurs. Program control is transferred to the label in case of an error during the execution of the BACKSPACE statement. |
BACKSPACE in a terminal file has no effect.
u must be connected for sequential access. Execution of a BACKSPACE statement on a direct-access file is not defined in the FORTRAN 77 Standard, and is unpredictable. We do not recommend using a BACKSPACE statement on a direct-access file or an append access file.
Execution of the BACKSPACE statement modifies the file position, as follows:
Prior to Execution |
After Execution |
Beginning of the file |
Remains unchanged |
Beyond the endfile record |
Before the endfile record |
Beginning of the previous record |
Start of the same record |
BACKSPACE 2 LUNIT = 2 BACKSPACE LUNIT
Example 2: Backspace with error trap:
INTEGER CODE BACKSPACE ( 2, IOSTAT=CODE, ERR=9 ) ... 9 WRITE (*,*) 'Error during BACKSPACE' STOP