# Fatal Error: Can't open module file 'first\_module.mod' for reading at (1): No such file or directory **URL:** \ **Category:** Uncategorized\ **Created:** [May 25, 2022, 2:03pm UTC](https://fortran-lang.discourse.group/t/fatal-error-cant-open-module-file-first-module-mod-for-reading-at-1-no-such-file-or-directory/3553 "2022-05-25T14:03:13Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![giraffe](https://avatars.discourse-cdn.com/v4/letter/g/f1d935/32.png) [@giraffe](https://fortran-lang.discourse.group/u/giraffe)\ **Post date:** [May 25, 2022, 2:03pm UTC](https://fortran-lang.discourse.group/t/fatal-error-cant-open-module-file-first-module-mod-for-reading-at-1-no-such-file-or-directory/3553/1 "2022-05-25T14:03:13Z")
From the below files, how do I create the first\_module.mod file requested by the compiler? File first\_module.f: ```auto MODULE FIRST_MODULE implicit none contains LOGICAL FUNCTION RUZE(CARD1,CARD2,LENGTH) IMPLICIT NONE INTEGER LENGTH CHARACTER CARD1*(*) CHARACTER, dimension (LENGTH:LENGTH) :: CARD2 RUZE = .FALSE. IF (CARD1(1:1).EQ.'$')THEN IF (CARD2(LENGTH) == ' ')THEN WRITE (*,*) 'STEP2 SUCCESSFUL' GOTO 10 ELSE WRITE (*,*) 'STEP2 NOT SUCCESSFUL' GOTO 20 ENDIF ELSE WRITE (*,*) 'DID NOT PERFORM STEP2' ENDIF 10 RUZE = .TRUE. 20 RETURN END SUBROUTINE MAKE_MOVE(STD) IMPLICIT NONE CHARACTER(*) :: STD(:) CHARACTER REPRESENT*10 IF(RUZE(REPRESENT(1:7),STD(1:7),7))THEN WRITE (*,*) 'STEP1 SUCCESSFUL' ELSE WRITE (*,*) 'STEP1 NOT SUCCESSFUL' ENDIF RETURN END END MODULE FIRST_MODULE ``` File test.f: ```auto Program PLAYING USE FIRST_MODULE IMPLICIT NONE INTEGER MOVES PARAMETER (MOVES=100) CHARACTER*15 BIGMOVE(MOVES) CALL MAKE_MOVE(BIGMOVE) End Program PLAYING ``` ```auto gfortran -u -g -c test.f test.f:2:9: USE FIRST_MODULE 1 Fatal Error: Can't open module file 'first_module.mod' for reading at (1): No such file or directory ``` ---
**Author:** ![Arjen](https://avatars.discourse-cdn.com/v4/letter/a/b9bd4f/32.png) [@Arjen](https://fortran-lang.discourse.group/u/Arjen)\ **Post date:** [May 25, 2022, 2:25pm UTC](https://fortran-lang.discourse.group/t/fatal-error-cant-open-module-file-first-module-mod-for-reading-at-1-no-such-file-or-directory/3553/2 "2022-05-25T14:25:25Z")
You first compile the source file containing the module first\_module. This will produce the .mod file and then the compiler can compile the second file. This type of dependency is quite common. Try: ```auto gfortran -c first_module.f gfortran -o mytest test.f first_module.o ``` (The reason for giving the program a different name than “test” is that under Linux shells “test” may be a builtin command. The default name “a.out” is not very informative in my opinion 🙂 ) ---
**Author:** ![alozada](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/alozada/32/298_2.png) [@alozada](https://fortran-lang.discourse.group/u/alozada)\ **Post date:** [May 25, 2022, 2:48pm UTC](https://fortran-lang.discourse.group/t/fatal-error-cant-open-module-file-first-module-mod-for-reading-at-1-no-such-file-or-directory/3553/3 "2022-05-25T14:48:14Z")
> [@giraffe](#): > > “[…]how do I create the first\_module.mod file requested by the compiler?[…]” You can also find useful information, with examples, about the procedures for building programs at [fortran-lang.org](http://fortran-lang.org), [Learn section](https://fortran-lang.org/learn/building_programs/linking_pieces). ---
**Author:** ![Pap](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/pap/32/1305_2.png) [@Pap](https://fortran-lang.discourse.group/u/Pap)\ **Post date:** [May 25, 2022, 2:55pm UTC](https://fortran-lang.discourse.group/t/fatal-error-cant-open-module-file-first-module-mod-for-reading-at-1-no-such-file-or-directory/3553/4 "2022-05-25T14:55:25Z")
`first_module.mod` doesn’t exist because the compiler just compiled `test.f`. You don’t mention `fist_module.f` in your compiling command thus it wasn’t compiled at all. The simplest and fastest solution is what @Arjen recommended. I personally prefer a makefile which makes things clear and it is more or less mandatory for larger projects as well. It is a good idea to get used to them. In your case, consider the following makefile (a little more generic and expandable): ```auto SRC_DIR = . OBJ_DIR = . EXE = ../test FC = gfortran FFLAGS = -std=f90 -O2 -Wall -Wextra FINCLUDES = LDFLAGS = LDLIBS = OBJS = \ $(OBJ_DIR)/first_module.o\ $(OBJ_DIR)/test.o.o all: $(OBJS) $(FC) $(FFLAGS) $(OBJS) $(LDFLAGS) $(LDLIBS) -o $(EXE) # ------------------------------------------------------------------------------ $(OBJ_DIR)/first_module.o: $(SRC_DIR)/first_module.f $(FC) $(FFLAGS) $(FINCLUDES) -c $(SRC_DIR)/first_module.f -o $@ $(OBJ_DIR)/test.o: $(OBJ_DIR)/first_module.o $(SRC_DIR)/test.f $(FC) $(FFLAGS) $(FINCLUDES) -c $(SRC_DIR)/test.f -o $@ # ------------------------------------------------------------------------------ ``` The most important part is the last one where it clearly states that to `compile test.f` you need `first_module.o`, meaning you tell the compiler it has to compile `first_module.f` _before_ attempting to compile `test.f`. This not only avoids errors like the one you got, but also gives the compiler enough information so that, if you just modify `test.f` later on, it will only compile that file and keep using the object code for first\_module created earlier. Furthermore, it makes parallel compilation in larger projects possible. Automated tools for Makefiles also exist, and you can use them instead, or you can use cmake, or other tools designed for that purpose, or even an IDE. If you want to get serious about programming, you will need one of those, so it is a good idea to get used to them even for small projects such as the one you posted.