ENVREAL() and envrealc()

Fortran version:

ENVREAL() is a Fortran wrapper calling the C envrealc()

    REAL FUNCTION ENVREAL( LNAME, DESCRIP, DEFAULT, STATUS )
        CHARACTER*(*)    LNAME   ! logical name to evaluate
        CHARACTER*(*)    DESCRIP ! description of the value
        REAL             DEFAULT ! default value (if LNAME not set, or empty)
        INTEGER          STATUS  ! for error/default-case detection

C version:

float envrealc( const char * lname       , 
                const char * description , 
                float        defaultval  ,
                int        * status )

Summary:

This function is a shell around the getenv() system call: find, log, and return the value of shell variable/logical name LNAME in the environment , and interpret it as REAL. Returns the DEFAULT if the logical name is not defined, is defined but has an empty value, or has an improper value. Writes a message to the log indicating the value returned -- and if the value was improper, writes a warning notice. STATUS takes the following values:

For Fortran-90 declarations and interface checking:

    USE M3UTILIO
    

See also

ENVDBLE,
ENVINT,
ENVSTR,
ENVYN,
NAMEVAL, and
SETENVVAR.

Preconditions:

#include "iodecl3.h" if called from C.

LNAME and DESCRIP have length at most 256. (NOTE: POSIX says that environment variables may have lengths this long.)

Fortran Usage:

Get a program-control parameter for logical name 'FOO' which defaults to 17.0, generating appropriate log messages, etc.:
...
setenv FOOFLAG True
...
/mydirectory/myprogram
... 
    ...
    INTEGER        FOO
    INTEGER        STATUS
    ...
    FOO = ENVREAL( 'FOO', 
 &             'Some control parameter or other, called FOO',
 &             17.0 ,
 &             STATUS )
    IF ( STATUS .GT. 0 ) THEN
        ... bad value for FOO; do something.
    END IF
    ...

C Usage:

Same as above, but test for defaults as well:
#include "iodecl3.h"
...
int    status ;
double value ;
...
value = envrealc( "FOO", 
                  "Here is where I put a description",
                  17.0 ,
                  & status ) )
if ( status > 0 ) 
    {
    ... stuff for bad (non-integer) value of environment variable FOO
    }
else if ( status == -1 ) 
    {
    ... stuff for empty-but-defined FOO
    }
else if ( status == -2 ) 
    {
    ... stuff for not-defined-at-all FOO
    }
... 
use value...


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