Manual Reference Pages - endfile (7fortran)

NAME

ENDFILE(7) - [NUMERIC] Absolute value

SYNOPSIS

endfile unit_number

DESCRIPTION

An ENDFILE(7f) ends or truncates a file at the current record.
Execution of an ENDFILE(7F) statement for a file connected for SEQUENTIAL ACCESS writes an endfile record as the next record of the file. The file is then positioned after the endfile record, which becomes the last record of the file.

o SEQUENTIAL ACCESS : After execution of an ENDFILE(7F) statement for a file connected for sequential access, a BACKSPACE(7F) or REWIND(7F) statement shall be used to reposition the file prior to execution of any data transfer input/output statement or ENDFILE(7F) statement.

o DIRECT ACCESS : For a file connected for DIRECT ACCESS, only those records before the endfile record are considered to have been written. Thus, only those records or additional records subsequently written shall be read during subsequent direct access connections to the file.

o STREAM ACCESS : Execution of an ENDFILE(7F) statement for a file connected for STREAM ACCESS causes the terminal point of the file to become equal to the current file position. Only file storage units before the current position are considered to have been written; thus only those file storage units shall be subsequently read. Subsequent stream output statements may be used to write further data to the file.

Execution of an ENDFILE(7F) statement for a file that is connected but does not exist creates the file; if the file is connected for sequential access, it is created prior to writing the endfile record.

OPTIONS

LUN A unit number of a connected file

EXAMPLES

An example of an ENDFILE(7f) statement is:

        program demo_endfile
        implicit none
        integer :: lun, i, j, iostat
        integer,parameter:: isz=10
           !
           ! create a little scratch file
           open(newunit=lun,file=’_scr.txt’, form=’formatted’)
           write(lun,’(i0)’)(100+i,i=1,isz)
           !
           ! write end of file after reading half of file
           rewind(lun)
           write(*,*)’rewind and read’,isz/2,’lines’
           read(lun,*)(j,i=1,isz/2)
           endfile lun ! will truncate line at current position
           !
           ! NOTE: backspace before writing any addition lines
           !       once an ENDFILE(7f) statement is executed
           ! backspace(lun)
           !
           ! rewind and echo remaining file
           rewind(lun)
           j=0
           do i=1,huge(0)-1
              read(lun,*,iostat=iostat)j
              if(iostat.ne.0)exit
              write(*,*)i,j
           enddo
           write(*,*)’number of lines in file was ’,isz,’, is now ’,i-1
           close(unit=lun,status=’delete’)
        end program demo_endfile

o	SEQUENTIAL ACCESS : After execution of an ENDFILE(7F) statement for a file connected for sequential access, a BACKSPACE(7F) or REWIND(7F) statement shall be used to reposition the file prior to execution of any data transfer input/output statement or ENDFILE(7F) statement.
o	DIRECT ACCESS : For a file connected for DIRECT ACCESS, only those records before the endfile record are considered to have been written. Thus, only those records or additional records subsequently written shall be read during subsequent direct access connections to the file.
o	STREAM ACCESS : Execution of an ENDFILE(7F) statement for a file connected for STREAM ACCESS causes the terminal point of the file to become equal to the current file position. Only file storage units before the current position are considered to have been written; thus only those file storage units shall be subsequently read. Subsequent stream output statements may be used to write further data to the file.

Manual Reference Pages - endfile (7fortran)

NAME

SYNOPSIS

DESCRIPTION

OPTIONS

EXAMPLES

SEE ALSO