C Library Functions - get_env (3)
NAME
get_env(3f) - [M_io:QUERY] a function returning the value of an environment variable (LICENSE:PD)
CONTENTS
Syntax
Description
Options
Returns
Examples
See Also
Author
License
SYNTAX
function get_env(NAME,DEFAULT,IERR=IERR) result(VALUE)
character(len=*),intent(in) :: NAME! ONE OF ... o character(len=*),intent(in),optional :: DEFAULT o real,intent(in),optional :: DEFAULT o integer,intent(in),optional :: DEFAULT o doubleprecision,intent(in),optional :: DEFAULT o logical,intent(in),optional :: DEFAULT
integer,intent(out),optional :: IERR
! ONE OF THE FOLLOWING, MATCHING TYPE OF DEFAULT o character(len=:),allocatable :: VALUE o integer :: VALUE o real :: VALUE o doubleprecision :: VALUE o logical :: VALUE
DESCRIPTION
Get the value of an environment variable or optionally return a default value when the environment variable is not set or is set to a blank string.The type returned is the same as the type of the default value.
OPTIONS
NAME name of environment variable DEFAULT value to return if environment variable is not set or set to an empty string. May be CHARACTER, REAL, INTEGER, LOGICAL or DOUBLEPRECISION. Defaults to a null CHARACTER value.
RETURNS
VALUE the value of the environment variable or the default. The type is the same as DEFAULT. If an error occurs and it is numeric, huge(0|0.0|0.0d0) is returned. For a LOGICAL type, Any environment variable value starting with F,f,N or n is .FALSE. and any value starting with Y,y,T or t is true. A leading period (".") is ignored. Anything else returns .false. .
IERR return error code. Must be specified with a keyword. It is zero if no error occurred.
EXAMPLES
Sample program:
program demo_get_env use M_io, only : get_env, getname character(len=*),parameter :: g=’(*(g0))’ integer :: ierr character(len=:),allocatable :: HOME !Basics HOME=get_env(’HOME’,’UNKNOWN’) write(*,’(a)’)HOME write(*,’(a)’)Get_env(’PATH’)!call this program setting STOP=RUN unless STOP=RUN !otherwise print various environment variable values !converted to various types if(get_env(’STOP’).eq.’RUN’)then write(*,g)repeat(’-’,80) write(*,g)get_env(’CHARACTER’,’string’) write(*,g)get_env(’INTEGER’,100) write(*,g)get_env(’REAL’,200.0) write(*,g)get_env(’DOUBLE’,300.0d0) write(*,g)get_env(’LOGICAL’,.true.)
write(*,g)repeat(’-’,80) write(*,g)get_env(’CHARACTER’,’string’,ierr=ierr) write(*,*)’ierr=’,ierr write(*,g)get_env(’INTEGER’,100,ierr=ierr) write(*,*)’ierr=’,ierr write(*,g)get_env(’REAL’,200.0,ierr=ierr) write(*,*)’ierr=’,ierr write(*,g)get_env(’DOUBLE’,300.0d0,ierr=ierr) write(*,*)’ierr=’,ierr write(*,g)get_env(’LOGICAL’,.true.) write(*,*)’ierr=’,ierr
write(*,g)repeat(’-’,80) write(*,g)get_env(’CHARACTER’) write(*,g)get_env(’HOME’) else write(*,g)repeat(’-’,80) call execute_command_line(’env STOP=RUN ’//getname()) call execute_command_line(’env STOP=RUN CHARACTER=aaaa & & INTEGER=1 REAL=2.3 DOUBLE=444444444444 ’//getname()) call execute_command_line(’env STOP=RUN CHARACTER=bbbb & & INTEGER=1 REAL=2.3 DOUBLE=44.555 ’//getname()) call execute_command_line(’env STOP=RUN CHARACTER=cccc & & INTEGER=asdf REAL=asdf DOUBLE=adsf ’//getname()) write(*,g)repeat(’-’,80) stop endif
end program demo_get_env
SEE ALSO
This duplicates system_getenv(3m_system) in most respects but avoids some interdependencies as M_system(3) currently requires a POSIX programming environment.get_environment_variable(3fortran), system_getenv(3m_system), set_environment_variable(3m_system), system_putenv(3m_system), system_clearenv(3m_system), system_initenv(3m_system), system_getenv(3m_system), system_unsetenv(3m_system)
AUTHOR
John S. Urban
LICENSE
Public Domain
| Nemo Release 3.1 | get_env (3) | February 23, 2025 |
