assign

NAME

assign − Assign customizations to Fortran file I/O

SYNOPSIS

assign [command-options] [customize-options] [filespec]

DESCRIPTION

The assign command customizes the behavior of Fortran I/O for a certain set of files or logical units (for example, it can swap bytes when using big-endian files on a little-endian computer). By issuing the command several times, you can dictate different customizations for each of several sets of files or units.

The command-options relate to the command itself; the customize-options describe the desired behavior, and the filespec describes which files or logical units those customizations apply to. Each command allows multiple customize-options, but no more than one command-option and one filespec.

The command works by storing information into a file that the Fortran library inspects before performing I/O. You must set the environment variable FILENV to the name of that file before you type the assign command, and it must remain set when the program runs.

The pathf95(1) compiler also provides compile-time options for swapping bytes that are simpler to use. Setting FILENV overrides the compiled-in choices.

FILESPEC

The filespec can be:

u:unit

The logical unit numbered unit.

f:filename

The file whose name is filename.

p:pattern

Every file whose name matches pattern, using the % symbol as a wildcard which matches zero or more characters.

	g:du		Every direct unformatted file (e.g., files opened using "access=’direct’ form=’unformatted’").
	g:su		Every sequential unformatted file (e.g., files opened using "access=’sequential’ form=’unformatted’").
	g:all		Every file.

COMMAND OPTIONS

	-R		Remove all customizations for the specified filespec. If no filespec is specified, remove all customizations.
	-I		Add this command to any previous ones. Normally each assign command erases the effect of all previous assign commands, even if they refer to a different set of files. To allow more than one command to take effect at the same time, all but the first command must use −I.
	-O		Erase the effect of previous assign commands before adding the current command. This is the default.
	-V		Display all assign commands now in effect.

CUSTOMIZATION OPTIONS

-a name

Use name as the actual file name for the file specified by filespec, overriding any name provided by the FILE= specifier in an OPEN statement.

-F conversion Convert the byte ordering of each record header

(a four-byte record length which appears at the beginning and end of each record) in a sequential unformatted file. It is allowed only with unformatted files. The option has no effect on the data itself (see the −N option for that). The conversion may be:

f77.mips

On a little-endian computer, use big-endian format for each record header.

f77.vax

On a big-endian computer, use little-endian format for each record header.

−N conversion

Convert the byte ordering of the data in an unformatted file. It is allowed only with unformatted files. For sequential unformatted files, which have record headers, you will usually want to use the −F option as well so that the record headers are also converted. The conversion may be:

On a little-endian computer, use big-endian format for the data.

ia64

On a big-endian computer, use little-endian format for the data.

−S on|off

The −S off option enables the use of commas in list-directed output on files specified by filespec. The default is −S on. For example, if the default output would be "4 5 6", −S off produces "4, 5, 6".

−y on|off

The −y off option allows the use of repetition factors in list-directed output on files specified by filespec. The default is −y on. For example, if the default output would be "4 4 4", −y off produces "3*4".

EXAMPLES

Assign name tmp to unit 8, removing any previous assign commands whether or not they relate to unit 8:

% assign -a tmp u:8

Assign name tmp to unit 8 without removing any previous assign commands:

% assign -I -a tmp u:8

Convert numeric data from big-endian format when reading file data, and convert numeric data to big-endian format when writing that file (note that if the file is sequential, its record headers will remain in little-endian form unless you also use the −F option):

% assign -I -N be f:data

Allow repetition factors in list-directed output on any file whose name begins with x and ends with y:

% assign -I -y off p:x%y

For all direct unformatted files, convert numeric data from big-endian format on input, and generate big-endian format on output:

% assign -I -N be g:du

For all sequential unformatted files, convert data from big-endian format on input, and generate big-endian format on output ( the −N option); do likewise with the record headers (the −F f77.mips option):

% assign -I -N be -F f77.mips g:su

Allow the use of repetition factors on standard output (unit 6):

% assign -I -y off u:6

USING ASSIGN WITH MPI

When using assign with MPI, make sure that the environment variable FILENV is properly defined and that the assign file is accessible by each process. The mpirun program is not going to set the environment variable for you, so you need to have a wrapper-script that sets it.

You can define FILENV in your .cshrc or .bashrc file with these commands:

For bash:

#The following will concatenate the line ’export FILENV=.assign’ to the #end of your .bashrc. The ${HOME}/ is so that you can use this from any #directory. % echo "export FILENV=.assign" >> ${HOME}/.bashrc

For csh:

#The following will concatenate the line ’setenv FILENV .assign’ to the #end of your .cshrc. The ${HOME}/ is so that you can use this from any #directory % echo "setenv FILENV .assign" >> ${HOME}/.cshrc

If you are using an MPI process with a daemon startup, define FILENV by passing environment variables through a daemon. This is often MPI implementation-dependent.

For example, LAM/MPI supports defining FILENV through the −x option on mpirun, so your commands would look something like this (in bash):

% export FILENV=.assign % mpirun -np 2 -x FILENV foo

This would launch the foo program on 2 processes, each aware of the FILENV variable.

ENVIRONMENT

FILENV

The location of the assign file.