getarg-getenv-workaround

A GETARG - GETENV WORK-AROUND FOR g77 ON CYGWIN (and other platforms too)

While Fortran77 on proper Linux provides a mechanism to read the command line and the environment (subroutines GETARG and GETENV, respectively), this option fails under CYGWIN as you may fail to locate the main.o object that is needed.

So you may be interested in a work-around. It's an obvious one.

A wrapper shell script copies first the command line and then the output of unix command env to a file. Then it starts the binary module. In order to give nice names, the wrapper will have the name of the program without a file extension, say, myprog and the binary module will be myprog.x

The command-line-and-env container will be given a simple name, x.args.

The Fortran program needs to open and process this file. We'll have its name hard-wired. However, the unit number is prone to conflict with the users' choices. So the unit number needs to have a redefining option.

To keep any repetitive burden on the programmer small, the compiler script shown below will generate the wrap-file from a template if it does not already exist in the target directory.

So first there is getarg.f
Note that the two well-known subroutines have changed their names: get_arg and get_env
the reason being that the linker may complain about duplicate symbols.

A main program may have the following code section

      character str*128   ! or whatever you anticipate as maximum

      call get_arg (1,str)

      call get_env ('HOME',str)

The default file unit number is 69. When GET_ARG is called for the first time, it tries to find a unit that has not been opened yet by sarting with 69 and incrementing with +1 as long as needed. To get control on this mechanism,

      integer close_argenv, open_argenv
      character str*128   ! or whatever you anticipate as maximum

      iu = open_argenv (68) ! for example. *)
      call get_arg (1,str)
      iu = close_argenv ()

*) If, however, 68 is already open, the next free unit will be used and the number returned by open_argenv.

The wrap script:

#!/bin/sh
prm=`echo "$1" | sed 's|$[^ ]*$.*|\1|'`
if [ x$prm = x-h ]; then
   echo "USAGE: wrap [-v] program parameters"
   echo "       -v   option to verify writing of parameters to file ./x.args"
   echo "OBS! writes to file ./x.args"
   exit
fi

verify=no

if [ x$prm = x-v ]; then
   verify=yes
   shift
fi

prog="$1"
shift
rm -f x.args
touch x.args

while [ ! x`echo $1 | sed 's|$[^ ]*$.*|\1|'` = x ]; do
   echo "$1" >> x.args
   shift
done

echo "-- ENVIRONMENT >" >> x.args
env >> x.args

if [ $verify = yes ]; then
   echo $prog
   cat x.args
fi

$prog
exit

The compiler script gfmb makes a script mymain (mymain.w if necesary) from a template named wrap.stub
wrap.stub looks like this:

#!/bin/csh
wrap progfile $*
exit

Repetition:
fcmd is a script whose home is the directory of a family of main programs that share most of their needs (calling libraries e.g.). The script is adapted to these needs (many times only the string collecting the libraries needs reworking.)
fcmd calls gfmb (if environment variable F77COMP is "g77"); gfmb should be in a directory on the current search path, e.g. $HOME/bin

The relevant lines in gfmb are

if [ ! -r ${BINP}/${fnp} ]; then
    sed 's|progfile|'${BINP}/${fnp}${FNOX}'|' /home/hgs/bin/wrap.stub > ${BINP}/${fnp}
    chmod u+x ${BINP}/${fnp}
    echo "wrap file written: ${BINP}/${fnp}"
fi

It might be necessary (Cygwin) to append a `.w´ to the wrap file's name. I.e. use ${fnp}.w instead of ${fnp} in the code above.
Above, FNOX would be set to .x by fcmd, fnp is the short form of the main program's name (e.g. mymain), and BINP the directory where to install ($HOME/bin e.g.).