char - C: correct usage of strtok_r

Question

How can I use strtok_r instead of strtok to do this?

char *pchE = strtok(NULL, " ");

Now I'm trying to use strtok_r properly... But sometimes I get problems with the strtol. I have a thread that I execute 10 times (at the same time).

char *savedEndd1;
char *nomeClass = strtok_r(lineClasses, " ", &savedEndd1);
char *readLessonS = strtok_r (NULL, " ", &savedEndd1);
char *readNTurma = strtok_r(NULL, " ",  &savedEndd1);

if (readNTurma==NULL)
printf("CLASS STRTOL begin %s %s
",nomeClass, readLessonS );
int numberNTurma = strtol(readNTurma, NULL, 10);

And I'm catching that readNTurma == NULL several times... Why is that? Cant understand why it comes NULL?

Answer 1

The documentation for strtok_r is quite clear.

The strtok_r() function is a reentrant version strtok(). The saveptr argument is a pointer to a char * variable that is used internally by strtok_r() in order to maintain context between successive calls that parse the same string.

On the first call to strtok_r(), str should point to the string to be parsed, and the value of saveptr is ignored. In subsequent calls, str should be NULL, and saveptr should be unchanged since the previous call.

So you'd have code like

char str[] = "Hello world";
char *saveptr;
char *foo, *bar;

foo = strtok_r(str, " ", &saveptr);
bar = strtok_r(NULL, " ", &saveptr);