Split string by a substring

问题

I have following string:

char str[] = "A/USING=B)";

I want to split to get separate A and B values with /USING= as a delimiter

How can I do it? I known strtok() but it just split by one character as delimiter.

回答1:

I known strtok() but it just split by one character as delimiter

Nopes, it's not.

As per the man page for strtok)(), (emphasis mine)

char *strtok(char *str, const char *delim);

[...] The delim argument specifies a set of bytes that delimit the tokens in the parsed string. [...] A sequence of two or more contiguous delimiter bytes in the parsed string is considered to be a single delimiter. [...]

So, it need not be "one character" as you've mentioned. You can using a string, like in your case "/USING=" as the delimiter to get the job done.

回答2:

As others have pointed out, you can use strstr from <string.h> to find the delimiter in your string. Then either copy the substrings or modify the input string to split it.

Here's an implementation that returns the second part of a split string. If the string can't be split, it returns NULL and the original string is unchanged. If you need to split the string into more substrings, you can call the function on the tail repeatedly. The first part will be the input string, possibly shortened.

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

char *split(char *str, const char *delim)
{
    char *p = strstr(str, delim);

    if (p == NULL) return NULL;     // delimiter not found

    *p = '\0';                      // terminate string after head
    return p + strlen(delim);       // return tail substring
}

int main(void)
{
    char str[] = "A/USING=B";
    char *tail;

    tail = split(str, "/USING=");

    if (tail) {
        printf("head: '%s'\n", str);
        printf("tail: '%s'\n", tail);
    }

    return 0;
}

回答3:

See this. I got this when I searched for your question on google.

In your case it will be:

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

int main (int argc, char* argv [])
{
    char theString [16] = "abcd/USING=efgh";
    char theCopy [16];
    char *token;
    strcpy (theCopy, theString);
    token = strtok (theCopy, "/USING=");
    while (token)
    {
        printf ("%s\n", token);
        token = strtok (NULL, "/USING=");
    }

    return 0;
}

This uses /USING= as the delimiter.

The output of this was:

abcd                                                                                                                                                                                                                      
efgh

If you want to check, you can compile and run it online over here.

来源：https://stackoverflow.com/questions/34942523/split-string-by-a-substring

标签

string

tokenize

strtok