macOS strtok

[farmerdoug]

If I input BD+05 378, the code knows what do to converting it to BD%2B+378 but if I enter vega, strtok returns vega and not NULL

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

int main (int argc, const char * argv[]) {
// http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=vega&submit=SIMBAD+search 
char *star, *path, *simbad, c, *token, plus = '+', *tmpstar;
int offset, i;
float Vmag;

FILE *file;

star = (char *)calloc(30, sizeof(char));
tmpstar = (char *)calloc(30, sizeof(char));
path = (char *)calloc(250, sizeof(char));
simbad = (char *)calloc(250, sizeof(char));
do
    {
   
    strcpy(path,"'http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=");

    printf("input star name or q to quit:\n");
    i = 0;
    fscanf(stdin,"%c", &c);
    while (c != '\n')
        {
        star[i++] = c;
        fscanf(stdin,"%c", &c);
        }
    star[i] = '\0';    
  
    
    
    if ((token = strtok(star,&plus)) != NULL)
        {printf("%s\n", token);
        strcpy(tmpstar, token);
        strcat(tmpstar, "%2B");
        token = strtok(NULL,&plus);
        printf("%s\n", token);
        strcat(tmpstar, token);
        strcpy(star, tmpstar);
        }
   
    i= 0;
    while (star[i++] != '\0')
        if (star[i-1] == ' ')
            star[i-1] = '+';
                            

     
    printf("%s\n", star);       
    if (strcmp(star,"q") == 0)
        return(99);
   
    strcat(path,star);
    strcpy(simbad, "curl ");
    strcat(simbad,path);
    strcat(simbad,"&submit=SIMBAD+search' > simbadout.txt ");
   
    system(simbad);
    strcpy(simbad,"grep \"<INPUT TYPE=\\\"hidden\\\" NAME=\\\"Coord\\\" VALUE=\\\"\" simbadout.txt > line.txt");
    system(simbad );
    if ((file = fopen("./line.txt", "r")) == NULL)
        printf("file not opened\n");
    
    fseek(file, 46, SEEK_SET);
    fgets(star,30,file);
    printf("%s\n",star);
    fclose(file);
    strcpy(simbad,"grep -b Fluxes simbadout.txt > line.txt");
    system(simbad );
     if ((file = fopen("./line.txt", "r")) == NULL)
        printf("file not opened\n");
    fscanf(file,"%d",&offset);
    printf("%d\n", offset);
     fclose(file);
     if ((file = fopen("./simbadout.txt", "r")) == NULL)
        printf("file not opened\n");

     fseek(file, offset, SEEK_SET);
   //   fgets(star,30,file);
   // printf("%s\n",star);
   // for (i = 0; i < 200; i++){
    fscanf(file,"%c", &c); 

     while (c != 'V')
        fscanf(file,"%c", &c); 
     
     fscanf(file,"%c", &c); 
    while (c != 'V')
        fscanf(file,"%c", &c);
     fscanf(file,"%c", &c);

    fscanf(file,"%s", star);
    printf("%s\n", star);
    
       
    
    

    }
while(strcmp(star,"q") != 0);
    

 return (0);
}

 

[gnasher729]

The second argument of strtok must be a null-terminated C string. &plus is not a null-terminated C string, but just a pointer to a single character. That can cause all kind of trouble.

Now if you _did_ pass "+" as the second argument, then you need to read the documentation of strtok carefully.

The first call will skip all "+" characters, then return NULL if there was nothing but "+" characters (shouldn't happen).
Then the first call returns either a string up to the first "+", or the complete string if there is no "+" afterwards.
The second call will return NULL if there was no "+" found in the first call, or it returns a string from the first to the second "+" and so on.

I suppose you would be happier using strchr or strstr to find the "+" character.

 

[farmerdoug]

Maybe it can be more elegant but it works. Thanks.

char *plus;
plus[0] = '+';
plus[1] = '\0';
 strcpy(tmpstar,star);
 
    
    if ((token = strtok(star,plus)) != NULL)
        if(strcmp(token,tmpstar) != 0)
        {
        printf("%s\n", token);
        strcpy(tmpstar, token);
        strcat(tmpstar, "%2B");
        token = strtok(NULL,plus);
        printf("%s\n", token);
        strcat(tmpstar, token);
        strcpy(star, tmpstar); 
        }

 

[chown33]

Maybe it can be more elegant but it works. Thanks.

char *plus;
plus[0] = '+';
plus[1] = '\0';

It's not a question of elegance, but correctness. That code has a serious bug.

char *plus; declares an uninitialized pointer.
plus[0] = '+'; stores data at whatever the uninitialized pointer happens to be pointing at.
plus[1] = '\0'; stores another byte of data, further obliterating some unknown memory location.

Try this:

char *plus = "+";

 

[farmerdoug]

I'm not exact sure what happened but the actual code reads
char plus[2];

but I like your coding better.
thanks