How to split a string to 2 strings in C

问题

I was wondering how you could take 1 string, split it into 2 with a delimiter, such as space, and assign the 2 parts to 2 separate strings. I\'ve tried using strtok() but to no avail.

回答1:

#include <string.h>

char *token;
char line[] = "SEVERAL WORDS";
char *search = " ";


// Token will point to "SEVERAL".
token = strtok(line, search);


// Token will point to "WORDS".
token = strtok(NULL, search);

Update

Note that on some operating systems, strtok man page mentions:

This interface is obsoleted by strsep(3).

An example with strsep is shown below:

char* token;
char* string;
char* tofree;

string = strdup("abc,def,ghi");

if (string != NULL) {

  tofree = string;

  while ((token = strsep(&string, ",")) != NULL)
  {
    printf("%s\n", token);
  }

  free(tofree);
}

回答2:

For purposes such as this, I tend to use strtok_r() instead of strtok().

For example ...

int main (void) {
char str[128];
char *ptr;

strcpy (str, "123456 789asdf");
strtok_r (str, " ", &ptr);

printf ("'%s'  '%s'\n", str, ptr);
return 0;
}

This will output ...

'123456' '789asdf'

If more delimiters are needed, then loop.

Hope this helps.

回答3:

char *line = strdup("user name"); // don't do char *line = "user name"; see Note

char *first_part = strtok(line, " "); //first_part points to "user"
char *sec_part = strtok(NULL, " ");   //sec_part points to "name"

Note: strtok modifies the string, so don't hand it a pointer to string literal.

回答4:

You can use strtok() for that Example: it works for me

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

int main ()
{
    char str[] ="- This, a sample string.";
    char * pch;
    printf ("Splitting string \"%s\" into tokens:\n",str);
    pch = strtok (str," ,.-");
    while (pch != NULL)
    {
        printf ("%s\n",pch);
        pch = strtok (NULL, " ,.-");
    }
    return 0;
}

回答5:

If you're open to changing the original string, you can simply replace the delimiter with \0. The original pointer will point to the first string and the pointer to the character after the delimiter will point to the second string. The good thing is you can use both pointers at the same time without allocating any new string buffers.

回答6:

If you have a char array allocated you can simply put a '\0' wherever you want. Then point a new char * pointer to the location just after the newly inserted '\0'.

This will destroy your original string though depending on where you put the '\0'

回答7:

You can do:

char str[] ="Stackoverflow Serverfault";
char piece1[20] = ""
    ,piece2[20] = "";
char * p;

p = strtok (str," "); // call the strtok with str as 1st arg for the 1st time.
if (p != NULL) // check if we got a token.
{
    strcpy(piece1,p); // save the token.
    p = strtok (NULL, " "); // subsequent call should have NULL as 1st arg.
    if (p != NULL) // check if we got a token.
        strcpy(piece2,p); // save the token.
}
printf("%s :: %s\n",piece1,piece2); // prints Stackoverflow :: Serverfault

If you expect more than one token its better to call the 2nd and subsequent calls to strtok in a while loop until the return value of strtok becomes NULL.

回答8:

This is how you implement a strtok() like function (taken from a BSD licensed string processing library for C, called zString).

Below function differs from the standard strtok() in the way it recognizes consecutive delimiters, whereas the standard strtok() does not.

char *zstring_strtok(char *str, const char *delim) {
    static char *static_str=0;      /* var to store last address */
    int index=0, strlength=0;       /* integers for indexes */
    int found = 0;                  /* check if delim is found */

    /* delimiter cannot be NULL
    * if no more char left, return NULL as well
    */
    if (delim==0 || (str == 0 && static_str == 0))
        return 0;

    if (str == 0)
        str = static_str;

    /* get length of string */
    while(str[strlength])
        strlength++;

    /* find the first occurance of delim */
    for (index=0;index<strlength;index++)
        if (str[index]==delim[0]) {
            found=1;
            break;
        }

    /* if delim is not contained in str, return str */
    if (!found) {
        static_str = 0;
        return str;
    }

    /* check for consecutive delimiters
    *if first char is delim, return delim
    */
    if (str[0]==delim[0]) {
        static_str = (str + 1);
        return (char *)delim;
    }

    /* terminate the string
    * this assignmetn requires char[], so str has to
    * be char[] rather than *char
    */
    str[index] = '\0';

    /* save the rest of the string */
    if ((str + index + 1)!=0)
        static_str = (str + index + 1);
    else
        static_str = 0;

        return str;
}

Below is an example code that demonstrates the usage

  Example Usage
      char str[] = "A,B,,,C";
      printf("1 %s\n",zstring_strtok(s,","));
      printf("2 %s\n",zstring_strtok(NULL,","));
      printf("3 %s\n",zstring_strtok(NULL,","));
      printf("4 %s\n",zstring_strtok(NULL,","));
      printf("5 %s\n",zstring_strtok(NULL,","));
      printf("6 %s\n",zstring_strtok(NULL,","));

  Example Output
      1 A
      2 B
      3 ,
      4 ,
      5 C
      6 (null)

You can even use a while loop (standard library's strtok() would give the same result here)

char s[]="some text here;
do {
    printf("%s\n",zstring_strtok(s," "));
} while(zstring_strtok(NULL," "));

来源：https://stackoverflow.com/questions/2523467/how-to-split-a-string-to-2-strings-in-c

标签

string

strtok