unable to send a char parameter from main to a function

why does this not work?

#include <stdio.h>
#include <stdlib.h>


char getFileMode(char charChanger) {

  char filetype; /*var to hold the value to be returned*/ 
  filetype = charSetter; /*set filetype to "l" if it is a symlink*/
 
return filetype;

}

int main(void){

char type = 0;

char     dir = 'd', 
        file = 'f', 
        slink = 'l', 
        charChanger=0;
        
        charChanger =  file;
        
    getFileMode(charChanger);
    
    printf("type is %c\n", type);
    
return 0;
}

charSetter is undefined for starters.

However, please define does not work. What EXACTLY are you trying to do?
Hint: it looks like you need to call stat() against an actual filename

#include <sys/stat.h>
char charSetter(char *filename)
{
     struct stat st;
     char retval='';
     if(stat(filename, &st ) == -1)
     {
             fprintf(stderr, "Cannot stat %s\n", filename);
             perror("");
             exit(1);
      }
      if (S_ISLNK(st.st_mode) )
          retval='l';
      return retval;
}

Hi Jim thank you for your reply!
I actually thought that what I had done was the problem but I think it is actually getopt() I will try to explain:
this first code takes care of a var that is set to either d,f or l (dir, file, or slink) the desired option in getopt().

char getFileMode(char charSetter) {
    char fileType = 0; /*var to hold the value to be returned*/ 
    charSetter=0;
    fileType = charSetter;    
    return fileType; /*end function */
}

Then I have a function where I do all the tests to see if I can open a dir do lstat and then test for S_ISDIR, S_ISREG and S_ISLNK.

All seems to work fine in it.

This is the prototype of the funcion.

void dirTreeWalker(char fileType, char *dirName, char charSetter);

This is what it does

1.1 open dir
   1.2  if dp == NULL print ERROR
 2.1 else while dp != NULL 
    2.2 if  not ".." and  not "."  lstat
    2.3 if  lstat(path, &info) < 0) print error
    2.4 if ((S_ISDIR(info.st_mode))&&(fileType == 'd')) print path
         else if ((S_ISREG(info.st_mode))&&( fileType == 'f')) print path
         else if ((S_ISLNK(info.st_mode))&&(fileType == 'l')) print path
    2.5 else print all thre options
    2.6 closedir

So long for that function, I have tested it on its own and it works.

However, and here is the problem I think...

When I use getopt like I do as follows I don't get to see the directories nor the files. It is as if charSetter does not get assigned any value.

    /*this set of vars for getopt*/
    int c;
    char *options = "t::dfl";
    extern char *optarg;
    extern int optind, optopt, opterr;
    char dir = 'd', 
        file = 'f', 
        slink = 'l', 
        charSetter = 0;

    /*this set of vars for the traversal and the test*/
    char fileType = 0;
    char *dirName = argv[argc-1];
    /* char *fileName =  */

while ((c = getopt(argc, argv, options)) != -1) {
    switch (c) {
        case 't':
            optarg = options;
            printf("Type is set: %c\n", charSetter);
            printf("option: %c\n",c);
            break;
            
        case 'd':
            printf("d is set\n");
            charSetter = dir;
            break;

        case 'f':
            printf("f is set\n");
            charSetter = file;
            printf("\ntype of file is f %c\n", fileType); /*test to be removed*/
            break;

        case 'l':
            printf("l is set\n");
            charSetter = slink;
            printf("\ntype of file is l %c\n", fileType); /*test to be removed*/
            break;

        case ':':
            printf("-%c without type\n", optopt);
            break;

        case '?':
            printf("unknown arg %c\n", optopt);
            fprintf(stderr, "Unrecognized option: -%c\n", optopt);
    }

}
    int i;
    for(i=1;i<argc;i++){
    printf("argv: %s\n",argv);
    }

    for (; optind < argc; optind++) {
     fileType = getFileMode(charSetter);
     dirTreeWalker(fileType, dirName, charSetter);
    }

We can't see your computer from here, you need to post the function contents too.

We don't even know what any of those global variables you're setting are.

It's a very bad idea to have a function that exists to do nothing but set global variables. Usually that means your programming model is a bit off somewhere. Honestly, this makes me suspect your other code as well, tested or not.

    charSetter=0;
    fileType = charSetter;   

Why do you bother passing charSetter if the very first thing you do is set it to zero? You'll never get anything but zero out of it.

Thank you all for the reply!

Sorry I copied that from my notepad in the wrong order... however, where I am having my problem is right here. When I run this part getopt() I don't get the return variable.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <dirent.h>
#include <errno.h>
#include <ctype.h>
#include <stdbool.h>

char getFileMode(char charSetter) {

    char fileType = 0; /*var to hold the value to be returned*/ 
    
    fileType = charSetter;
    
    return fileType; /*end function */
}

int main(int argc, char *argv[]) {

    /*this set of vars for getopt*/
    int c;
    char *options = "t::dfl";
    extern char *optarg;
    extern int optind, optopt, opterr;
    char dir = 'd', 
        file = 'f', 
        slink = 'l', 
        charSetter = 0;
    
    /*this set of vars for the traversal and the test*/
    char fileType = 0;
    char *dirName = argv[argc-1];

    if (argc < 2) {
        printf("mfind [-t type] start1 [start2 ...] name \n"); /*usage*/
    }

while ((c = getopt(argc, argv, options)) != -1) {
    switch (c) {
        case 't':
            optarg = options;
            printf("Type is  set to: %c\n", charSetter); /*should be zero*/
            printf("option: %c\n",c);
            break;
            
        case 'd':
            printf("d is set\n");
            charSetter = dir;
            break;

        case 'f':
            printf("f is set\n");
            charSetter = file;
            
            break;

        case 'l':
            printf("l is set\n");
            charSetter = slink;
            
            break;

        case ':':
            printf("-%c without type\n", optopt);
            break;

        case '?':
            printf("unknown arg %c\n", optopt);
            fprintf(stderr, "Unrecognized option: -%c\n", optopt);
    }

}
    int i;
    for(i=1;i<argc;i++){
    printf("argv: %s\n",argv);
    }

    for (; optind < argc; optind++) {
     fileType = getFileMode(charSetter);
        printf("the filetype is %c", fileType);
    }

return (0);
}

I was trying to do something like this but with getopt() in the program below when I set the values for cahrSetter manually it works fine.

#include <stdio.h>
#include <stdlib.h>


char getFileMode(char charChanger) {

  printf("charChanger has  %c\n", charChanger);
  
  char *filetype; /*var to hold the value to be returned*/ 
  
  filetype = charChanger; /*set filetype to 'l'*/
  
return filetype;

}

int main(void){

char type = 0;

char     dir = 'd', 
        file = 'f', 
        slink = 'l', 
        charChanger=0;
        
    charChanger =  file;
    type = getFileMode(charChanger);
    printf("type is %c\n", type);
    
return 0;
}

---------- Post updated at 11:04 AM ---------- Previous update was at 10:33 AM ----------

Sorry guys for my lack of attention ... it seems that I had not included the library

#include <getopt.h>

However, running the program see that the type is set to ^@ which does not make sense if I for example choose -td in which case the type should be 'd'.

I think you're very confused about variables, assignments, and return values, not just how getopt works. I continue to suspect the existence of latent bugs in your treewalker function, whether it works for you right now or not. Please post your entire code, not just the bits you think I need to know.

Your 'dir', 'file', and 'slink' variables are useless, you already know what 'c' is.

You shouldn't be setting optarg, you should be using optarg.

I still cannot fathom the purpose of your getFileMode function. You just return the same value you get, after setting a local variable, which changes nothing outside the function. What is it supposed to be doing?

switch (c) {
        case 't':
            // c isn't an ASCII 0, it's an ascii NULL.  If you want it to print 0,
            // initialize c to c='0' at the start of main.
            printf("Type is  set to: %c\n", charSetter); /*should be zero*/

            // the option string appears in optarg.
            printf("option:  %s\n", optarg);
            break;
            
        case 'd':
        case 'f':
        case 'l':
            charSetter=c;
            printf("%c is set\n", charSetter);
            break;
        default:
            fprintf(stderr, "Uknown option\n");
            exit(1);
        }

---------- Post updated at 10:58 AM ---------- Previous update was at 10:55 AM ----------

If your variables were an attempt to organize it, I think enums are closer to what you want. They even work in switch statements.

enum
{
        TYPE_DIR='d',
        TYPE_FILE='f', 
        TYPE_SLINK='l',
        TYPE_T='t',
};

...

switch (c) {
        case TYPE_T:
            // c isn't an ASCII 0, it's an ascii NULL.  If you want it to print 0,
            // initialize c to c='0' at the start of main.
            printf("Type is  set to: %c\n", charSetter); /*should be zero*/

            // the option string appears in optarg.
            printf("option:  %s\n", optarg);
            break;
            
        case TYPE_DIR:
        case TYPE_FILE:
        case TYPE_SLINK:
            charSetter=c;
            printf("%c is set\n", charSetter);
            break;
        default:
            fprintf(stderr, "Uknown option\n");
            exit(1);
        }

Hi Corona,

Thank you much for the explanation... you are right I am very confused and specially with pointers :-/ but hopefully I will some day get there... I think I have partially solved the problem... I did not understand how getopt worked and yes I gues 'c' was the return value.

In any case this is what I wanted to do ... sorry for not posting it before but I really wanted to give it a try before. What it does is it parses options and it prints either dir, file, or slink accordingly.

Well, yes -- but the function, what is it for?

Hi again, and thank you for the explanation... the function was to send to the treeWalker function the values that getopt sends instead, that is, the input for treeWalker ,

void dirTreeWalker(char fileType, char *dirName) 

in other words I was trying to "set getopt", just like you said , instead of using it. As it is now it works fine just by using getopt instead of trying to set it as I was doing.

while ((c = getopt(argc, argv, options)) != -1) {
    switch(c) {
    case 't':
        printf("t is set\n");
        break;
        
    case 'd':
        printf("d is set\n");
        fileType = 'd';
        printf("filename is %c\n", fileType);
        break;
    case 'f':
        printf("f is set\n");
        fileType = 'f';
        printf("filename is %c\n", fileType);
        break;
/*and so on*/