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Fortran Library Reference

fseek: Reposition a File on a Logical Unit

The function is called by:

INTEGER*4 fseek

n = fseek( lunit, offset, from )

lunit

INTEGER*4

Input  

Open logical unit  

offset

INTEGER*4

or

INTEGER*8

Input  

Offset in bytes relative to position specified by from

An INTEGER*8 offset value is required when compiled for a 64-bit environment, such as Solaris 7, with -xarch=v9. If a literal constant is supplied, it must be a 64-bit constant, for example: 100_8

from

INTEGER*4

Input  

0=Beginning of file  

1=Current position  

2=End of file  

Return value 

INTEGER*4

Output  

n=0: OK; n>0: System error code

Note -

On sequential files, following a call to fseek by an output operation (e.g. WRITE) causes all data records following the fseek position to be deleted and replaced by the new data record (and an end-of-file mark). Rewriting a record in place can only be done with direct access files.

Example: fseek()--Reposition MyFile to two bytes from the beginning 

    INTEGER*4 fseek, lunit/1/, offset/2/, from/0/, n
    open( UNIT=lunit, FILE='MyFile' )
    n = fseek( lunit, offset, from )
    if ( n .gt. 0 ) stop 'fseek error'
    end
:

Example: Same example in a 64-bit environment and compiled with -xarch=v9: 

    INTEGER*4 fseek, lunit/1/,  from/0/, n 
    INTEGER*8 offset/2/
    open( UNIT=lunit, FILE='MyFile' )
    n = fseek( lunit, offset, from )
    if ( n .gt. 0 ) stop 'fseek error'
    end