Split string using more than one char as delimeter - c

Question

Let's say I have a string "file1.h: file2.c,file3.cpp" and I want to split it into "file1.h" and "file2.c,file3.cpp" - that is using : (: and whitespace) as delimiter. How can I do it?
I tried this code with no help:
int main(int argc, char *argv[]) {
char str[] = "file1.h: file2.c,file3.cpp";
char name[100];
char depends[100];
sscanf(str, "%s: %s", name, depends);
printf("Name: %s\n", name);
printf("Deps: %s\n", depends);
}
And the output I get is:
Name: file1.h:
Deps:

Answer 1

What you seem to need is strtok(). Read about it in the man page. Related quote from C11, chapter §7.24.5.8
A sequence of calls to the strtok function breaks the string pointed to by s1 into a
sequence of tokens, each of which is delimited by a character from the string pointed to
by s2. [...]
In your case, you can use a delimiter like
char * delim = ": "; //combination of : and a space
go get the job done.
Things to mention additionally,
the input needs to be modifiable (which is, in your case) for strtok()
and it actually destroys the input fed to it, keep a copy around if you need the actual later.

Answer 2

This is an alternative way to do it, it uses strchr(), but this assumes that the input string always has the format
name: item1,item2,item3,...,itemN
Here is the program
#include <string.h>
#include <stdio.h>
int
main(void)
{
const char *const string = "file1.h: file2.c,file3.cpp ";
const char *head;
const char *tail;
const char *next;
// This basically makes a pointer to the `:'
head = string;
// If there is no `:' this string does not follow
// the assumption that the format is
//
// name: item1,item2,item3,...,itemN
//
if ((tail = strchr(head, ':')) == NULL)
return -1;
// Save a pointer to the next character after the `:'
next = tail + 1;
// Strip leading spaces
while (isspace((unsigned char) *head) != 0)
++head;
// Strip trailing spaces
while (isspace((unsigned char) *(tail - 1)) != 0)
--tail;
fputc('*', stdout);
// Simply print the characters between `head' and `tail'
// you could as well copy them, or whatever
fwrite(head, 1, tail - head, stdout);
fputc('*', stdout);
fputc('\n', stdout);
head = next;
while (head != NULL) {
tail = strchr(head, ',');
if (tail == NULL) {
// This means there are no more `,'
// so we now try to point to the end
// of the string
tail = strchr(head, '\0');
}
// This is basically the same algorithm
// just with a different delimiter which
// will presumably be the same from
// here
next = tail + 1;
// Strip leading spaces
while (isspace((unsigned char) *head) != 0)
++head;
// Strip trailing spaces
while (isspace((unsigned char) *(tail - 1)) != 0)
--tail;
// Here is where you can extract the string
// I print it surrounded by `*' to show that
// it's stripping white spaces
fputc('*', stdout);
fwrite(head, 1, tail - head, stdout);
fputc('*', stdout);
fputc('\n', stdout);
// Try to point to the next one
// or make head `NULL' if this is
// the end of the string
//
// Note that the original `tail' pointer
// that was pointing to the next `,' or
// the end of the string, has changed but
// we have saved it's original value
// plus one, we now inspect what was
// there
if (*(next - 1) == '\0') {
head = NULL;
} else {
head = next;
}
}
fputc('\n', stderr);
return 0;
}
It's excessively commented to guide the reader.

Answer 3

As Sourav says, you really need to use strtok for tokenizing strings. But this doesn't explain why your existing code is not working.
The answer lies in the specification for sscanf and how it handles a '%s' in the format string.
From the man page:
s Matches a sequence of non-white-space characters;
So, the presence of a colon-space in your format string is largely irrelevant for mathcing the first '%s'. When sscanf sees the first %s it simply consumes the input string until a whitespace character is encountered, giving you your value for name of "file1.h:" (note the inclusion of the colon).
Next it tries to deal with the colon-space sequence in your format string.
Again, from the man page
The format string consists of a sequence of directives which describe how to process the sequence of input characters.
The colon-space sequence does not match any known directive (i.e. "%" followed by something) and thus you get a matching failure.
If, instead, your format string was simply "%s%s", then sscanf will get you almost exactly what you want.
int main(int argc, char *argv[]) {
char str[] = "file1.h: file2.c,file3.cpp";
char name[100];
char depends[100];
sscanf(str, "%s%s", name, depends);
printf("str: '%s'\n", str);
printf("Name: %s\n", name);
printf("Deps: %s\n", depends);
return 0;
}
Which gives this output:
str: 'file1.h: file2.c,file3.cpp'
Name: file1.h:
Deps: file2.c,file3.cpp
At this point, you can simply check that sscanf gave a return value of 2 (i.e. it found two values), and that the last character of name is a colon. Then just truncate name and you have your answer.
Of course, by this logic, you aren't going to be able to use sscanf to parse your depends variable into multiple strings ... which is why others are recommending using strtok, strpbrk etc because you are both parsing and tokenizing your input.

Answer 4

Well, I am pretty late. I do not have much knowledge on inbuilt functions in C. So I started writing a solution for you. I don't think you need this now. But, anyway here it is and modify it as per your need. If you find any bug feel free to tell.