Splitting “String” into characters in C

Question

I am taking a beginner's course in C, and trying to wrap my head around "strings". I have previously programmed in Java, so it is a bit confusing.

I am wondering how to split a "string" into characters , so as to be able to remove certain characters. I have written code for a linked list, with each node holding a data value, as well as a next pointer (calling it node_line, as it holds lines).

typedef struct node {
    char *data;
    struct node *next;
} node_line;

This works without problems, and I can traverse the entire list and print out each element:

void print_list(node_line head) {
    node_line * current = head;
    while(current != NULL) {
          printf("%s\n", current->data);
          current = current->next;
    }
}

However, I am having problems with converting the "string" in current->data into characters. That is, reading one character at a time.

For instance, I want to write a program that removes all the vowels in a "string". I have managed to solve this when reading a file, using the getc() function. However, I can't seem to do so with the text in current-> data.

    int c;
    while((c = getc(f)) != EOF) {
        //REMOVE
        if(c=='a' || c=='e' || c=='i' || c=='o' || c=='u' || c=='y') {
            printf("");  //Remove the vowel
        }
        else {
            putchar(c); //Write out one character at the time.   
        }
    }

I imagine it being something like:

while ((c = getc(current->data) != NULL) { ... }

Any help, tips, etc. are highly appreciated!

Answer 1

getc is for reading from files . To access chars in a char * buffer (string) you would typically do something like this:

for (const char * p = current->data; *p != '\0'; ++p)
{
    char c = *p;
    if (c=='a' || c=='e' || c=='i' || c=='o' || c=='u' || c=='y') {
       ...
    }
}

Or if you prefer explicit array indexing rather than pointers:

const char * s = current->data;
for (int i = 0; i < strlen(s); ++i)
{
    char c = s[i];
    if (c=='a' || c=='e' || c=='i' || c=='o' || c=='u' || c=='y') {
       ...
    }
}

Answer 2

void print_list(node_line head) {

should be

void print_list(node_line *head) {

getc:

Returns the character currently pointed by the internal file position indicator of the specified stream.

That's not what you want, use pointer arithmetic:

char *s = current->data;

while (*s) {
    if(*s=='a' || *s=='e' || *s=='i' || *s=='o' || *s=='u' || *s=='y') {
        printf("");  //Remove the vowel
    }
    else {
        putchar(*s); //Write out one character at the time.   
    }
    s++;
}

or better:

char *s = current->data;

while (*s) {
    if(*s!='a' && *s!='e' && *s!='i' && *s!='o' && *s!='u' && *s!='y') {
        putchar(*s); //Write out one character at the time.   
    }
    s++;
}