Fortran read last line from file series#
Fortran read last line from file windows#

Unit: 100 File: ftn2idl.dat6 % Execution halted at $MAIN$( 0). FREE_LUN, lunД®xecuting these IDL statements produces the output: 0.00000 1.00000 2.00000 3.00000 4.00000 % READU: End of file encountered. FOR I = 0, 4 DO BEGIN Read a row of data. data = FLTARR( 5, /NOZERO) OPENR, lun, 'ftn2idl.dat', /GET_LUN, /F77_UNFORMATTED One row at a time. For example, consider the following attempt to read the above data file one row at a time: Create an array to contain one row of the FORTRAN array. PRINT, dataД®xecuting these IDL statements produces the following output: 0.00000 1.00000 2.00000 3.00000 4.00000 5.00000 6.00000 7.00000 8.00000 9.00000 10.0000 11.0000 12.0000 13.0000 14.0000Д«ecause unformatted data produced by FORTRAN unformatted WRITE statements on an operating system that uses stream files are interspersed with extra information before and after each logical record, it is important that the IDL program read the data in the same way that the FORTRAN program wrote it. READU, lun, data Release the logical unit number and close the fortran file. OPENR, lun, 'ftn2idl.dat', /GET_LUN, /F77_UNFORMATTED Read the data in a single input operation. The F77_UNFORMATTED keyword is necessary so that IDL will know that the file contains unformatted data produced by a UNIX FORTRAN program. data = FLTARR( 5, 3) Open the fortran-generated file. The following IDL statements can be used to read this file and print out its contents: Create an array to contain the fortran array. Running this program creates the file ftn2idl.dat containing the unformatted array.

Fortran read last line from file windows#

The following FORTRAN program, when run on a UNIX or Microsoft Windows system (that is, an operating system that uses stream files), produces a file containing a five-column by three-row array of floating-point values with each element set to its one-dimensional subscript: PROGRAM ftn2idl INTEGER i, j REAL data( 5, 3) OPEN( 1, FILE= 'ftn2idl.dat', FORM= 'unformatted') DO 100 j = 1, 3 DO 100 i = 1, 5 data(i,j) = ((j - 1) * 5) + (i - 1) print *, data(i,j) 100 CONTINUE WRITE( 1) data END Note: Direct-access FORTRAN I/O does not write data using logical records, but transfers binary data to or from the file. When writing unformatted Fortran files, IDL will continue to use 32-bit record markers.

When reading FORTRAN data, IDL will attempt to recognize the presence of 64-bit record markers and switch to the appropriate format. Note: On 64-bit machines, some Fortran compilers will insert record markers that are 64-bit integers instead of the standard 32-bit integers. Use the F77_UNFORMATTED keyword if your IDL program is reading data that contain embedded longword logical record separators, or if your program is writing data that will be read by a FORTRAN program that reads unformatted sequential files. Similarly, IDL can write data using the logical record format using the F77_UNFORMATTED keyword. When a file is opened with this keyword, IDL interprets the longword counts properly and is able to read the logical records.

The F77_UNFORMATTED keyword to the OPEN procedures informs IDL that the file contains unformatted data demarcated by logical record identifiers.

Fortran read last line from file series#

This mechanism allows FORTRAN-generated data files that treat data as a series of logical records to be read on platforms that use stream files. In order to reconcile the FORTRAN need for logical records with these stream files, FORTRAN compilers for UNIX and Microsoft Windows provide a mechanism to add a longword integer count of the number of bytes in each logical record. In contrast, the UNIX and Microsoft Windows operating systems supported by IDL treat files as an uninterrupted stream of bytes. This system works well for operating systems like VMS, which organize files into records and can thus keep track of where logical blocks of data begin and end.

To read data, the FORTRAN program asks for the next logical record from an open file the operating system is then responsible for determining how much data should be retrieved from the file. The standard FORTRAN unformatted sequential file input/output mechanism performs file input and output by reading and writing blocks of data from (or to) a file as logical records.