remove characters from a c string

Question

Hello,

gcc 4.4.4 c89

I am reading in from a text file and the text file consists of names in double quotes.

"Simpson, Homer"
etc

However, I want to remove the double quotes from the string.

This is how I have done it, but I am not sure its the best way.

int get_string(FILE *in, char *temp)
{
    char *quote = NULL;
    /* Get the first line */
    fgets(temp, STRING_SIZE, in);
    printf("temp before [ %s ]\n", temp);
    /* Find the second quote */
    if((quote = strrchr(temp, '"')) == NULL) {
        fprintf(stderr, "Text file incorrectly formatted\n");
        return FALSE;
    }
    /* Replace with a nul to get rid of the second quote */
    *quote = '\0';

    /* Move the pointer to point pass the first quote */
    temp++;
    printf("temp after [ %s ]\n", temp);
    return TRUE;
}

Many thanks for any suggestions,

Answer 1

No, this won't work. You are changing the parameter temp, but the calling function will still have an old value. The temp outside the function will point to the opening quote. You ought to move the characters in your buffer.

However I would suggest allocating the buffer in heap and returning a pointer to it, letting the caller free the buffer when needed. This seems to be a cleaner solution. Again, this way you won't rely on the caller to pass a sufficiently large buffer.

In general, a robust reading lines from a text file is not a trivial task in C, with its lack of automatic memory allocating functions. If possible to switch to C++, I would suggest trying much simpler C++ getline.

Answer 2

is all lines look that way why not simple remove the first and the last char?

quote++; // move over second char
quote[strlen(quote)-1]='\0'; // remove last char

Answer 3

Suppose

string="\"Simpson, Homer\""

then

string_without_quotes=string+1;

string_without_quotes[strlen(string)-2]='\0';

ready!

Answer 4

char *foo(char *str, int notme)
{
    char *tmp=strdup(str);
    char *p, *q;
    for(p=str, q=tmp; *p; p++)
    {
       if((int)*p == notme) continue;
       *q=*p;
       q++;
    }
    strcpy(str, tmp);
    free(tmp);
    return str;
}

simple generic remove a char

Answer 5

Don't know if this will help, it is a simple tokenizer i use

#include <stdlib.h>
#include <string.h>

int token(char* start, char* delim, char** tok, char** nextpos, char* sdelim, char* edelim) {
    // Find beginning:
    int len = 0;
    char *scanner;
    int dictionary[8];
    int ptr;

    for(ptr = 0; ptr < 8; ptr++) {
        dictionary[ptr] = 0;
    }

    for(; *delim; delim++) {
        dictionary[*delim / 32] |= 1 << *delim % 32;
    }

    if(sdelim) {
        *sdelim = 0;
    }

    for(; *start; start++) {
        if(!(dictionary[*start / 32] & 1 << *start % 32)) {
            break;
        }
        if(sdelim) {
            *sdelim = *start;
        }
    }

    if(*start == 0) {
        if(nextpos != NULL) {
            *nextpos = start;
        }
        *tok = NULL;
        return 0;
    }

    for(scanner = start; *scanner; scanner++) {
        if(dictionary[*scanner / 32] & 1 << *scanner % 32) {
            break;
        }
        len++;
    }

    if(edelim) {
        *edelim = *scanner;
    }

    if(nextpos != NULL) {
        *nextpos = scanner;
    }

    *tok = (char*)malloc(sizeof(char) * (len + 1));

    if(*tok == NULL) {
        return 0;
    }

    memcpy(*tok, start, len);
    *(*tok + len) = 0;


    return len + 1;
}

The parameters are:

• char* start, (pointer to the string)
• char* delim, (pointer to the delimiters used to break up the string)
• char** tok, a reference (using &) to a char* variable that will hold the toke
• char** nextpos, a reference (using &) to a char* variable that will hold the position after the last token.
• char* sdelim, a reference (using &) to a char variable that will hold the value of the -start delimiter
• char* edelim, a reference (using &) to a char varaible that will hold the value of the end delimiter

The last three are optional.

Pass in the start address, the delimeter is a ", and pass reference to a char * to hold the actual middle string.

The result is a newly allocated string so you have to free it.

int get_string(FILE *in, char *temp)
{
    char *token = NULL;
    /* Get the first line */
    fgets(temp, STRING_SIZE, in);
    printf("temp before [ %s ]\n", temp);
    /* Find the second quote */
    int length = token(temp, "\"", &token, NULL, NULL, NULL)

    // DO STUFF WITH THE TOKEN
    printf("temp after [ %s ]\n", token);
    // DO STUFF WITH THE TOKEN

    // FREE IT!!!
    free(token);
    return TRUE;
}

The tokenizer is a multipurpose tool that can be used in a crap ton of places, this being a very small example.