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Well.. I have a doubt on my code.. how can I extract content from a string like this "type=1;ammount=1212;name=motorbike;"
I want to extract the content of type, ammount and name for example so I can use it later.. any examples or ideas? examples will be appreciated =)
Yep. Several ideas. You could use strtok() (which will be immediately followed by Elysia's pushing of her strtok()--which is good. Use either hers or the standard c one. I don't care) and a subsequent call to either sscanf() or strchr() then sscanf().
Divide and conquer.
Code:Find next semicolon...
Find next equal sign...
Left of equal sign is key
Right of equal sign is value
Repeat until no more semicolons.
If you want a specific example (though granted in another programming language) just google "parsing cookies."
I've read in the forum this..
What if I need 3 things to parse, do I have to add antoher NULL in the first parameter of strtok?Code:char *str; // <- Why is it a pointer?
char line[]="somefile:anotherfile";
while (str != NULL) {
str = strtok(line, ":"); // <- this will store "somefile"
str = strtok(NULL, ":"); // <- now str will contain "anotherfile"
}
And I have 2 parameters the start and the end.. what do you suggest me to do?
The example you are using is NOT a good one!
Better:
Notice that you only pass "string" as the first argument to strtok the first time.Code:#include <stdio.h>
#include <string.h>
int main() {
char string[]="type=1;ammount=1212;name=motorbike;", *tok;
tok=strtok(string,";");
puts(tok);
while((tok=strtok(NULL,";")) != NULL) puts(tok);
}
Only the first one should use the actual char variable. The loop in your example will not work because it reinitializes strtok at every pass.Quote:
Originally Posted by lautarox
My output looks like this:
type=1
ammount=1212
name=motorbike
If it were me doing this sort of program, and believe me I have had to parse many a string like that in the past.
Example:
Then parse out the semicolons to split appart each "variable" then work your magic to determine the nature of the variable. You could also make the variable structure a linked list or something too. But its just a suggestion. I don't know how static your string is going to be. That kind of makes a difference.Code:enum E_VARIABLE_TYPE =
{
EVT_UNK,
EVT_INT,
EVT_STR,
EVT_FLT
};
struct variable
{
enum E_VARIABLE_TYPE type;
const char *name;
union
{
const char *str_val;
int int_val;
float flt_val;
}; /* This isn't standard as far as I am aware. But it may work for you.
* If not, just resolve the anonymous union error your compiler throws up.
*/
};
NULL means "use the same string you used the last time, oh, and start from where the last one left off". So the first time you call strtok, you pass the string along; after that, you pass in NULL so that the altered copy is used henceforward.Quote:
Originally Posted by lautarox
Ok well since it merits being said given your example of strtok() that you found. This is a revised version of strtok() by the lovely Elysia. You may wish to use hers instead since it won't damage the original input data. Though in honesty, when I have done things like this in my projects, changing the original data was not an issue at all.
Why this doesn't imput what's between "dude=" and ";"
Code:char lol[]="dude=matt;car=toyota;", *p;
p=strtok(lol, "dude=");
p=strtok(NULL, ";");
puts(p);
strtok doesn't use multicharacter tokenisers. When you use "dude=" as the second argument, strtok will look for one of 'd', 'u', 'd', 'e', or '=' to stop the first strtok. And of course it finds it right away, so it only throws away "d", not "dude=".
You probably want to use "=" as the first tokeniser and ";" as the second.
Because you are using strtok() incorrectly....
bleh... I hate writing out examples for people like this...
Example:
There are many imperfections in this code... It doesn't handle hex values (which it easily could). It doesn't necessarily handle negative ints correctly, which again, its an easy fix. But its a start.Code:
#include <ctype.h>
#include <stdlib.h>
#include <stdio.h>
/* First let me copy and paste my data structure from an earlier post */
enum E_VARIABLE_TYPE =
{
EVT_UNK,
EVT_INT,
EVT_STR,
EVT_FLT
};
struct variable
{
enum E_VARIABLE_TYPE type;
const char *name;
union
{
const char *str_val;
int int_val;
float flt_val;
}; /* This isn't standard as far as I am aware. But it may work for you.
* If not, just resolve the anonymous union error your compiler throws up.
*/
/* Let me make this a linked list for simplicity. */
struct variable *next;
};
struct variable *parse(char *buffer)
{
struct variable *head = malloc(sizeof(*head)), *node = head;
if(!head)
return 0;
for(buffer = strtok(buffer, ";"); buffer; strtok(NULL, "';"))
{
if(!node)
{
fputs("Cannot complete the parsing! Out of memory!\n", stderr);
return head;
}
node->name = buffer;
node->next = malloc(sizeof(*node));
node = node->next;
}
if(node)
node->next = 0;
if(head)
/* Now parse each segment of data */
for(node = head; node; node = node->next)
{
char *data = strchr(node->name, '=');
if(data)
{
*data++ = 0;
node->str_val = data;
node->type = EVT_INT;
/* Now the type needs to be determined */
for(;*data;++data)
{
if(isalpha(*data))
{
node->type = EVT_STR;
break;
}
if(ispunct(*data))
{
node->type = EVT_FLT;
}
}
switch(node->type)
{
case EVT_INT:
node->int_val = strtol(node->str_val, NULL, "10");
break;
case EVT_FLT:
node->flt_val = atof(node->str_val);
break;
}
}
}
return head;
}
//[EDIT]
/* For the hell of it... */
void revert(char *buffer, size_t len, struct variable *node)
{
size_t offset;
for(;node; node = node->next)
{
switch(node->type)
{
case EVT_INT:
offset = snprintf(buffer, len, "%s=%d;", node->name, node->int_val);
break;
case EVT_FLT:
offset = snprintf(buffer, len, "%s=%f;", node->name, node->flt_val);
break;
case EVT_STR:
offset = snprintf(buffer, len, "%s=%s;", node->name, node->str_val);
break;
}
buffer += offset;
len -= offset;
}
}
//[/EDIT]
Imagine if I get 12233 from the extraction, how can i convert it into a integer?
Sorry, I didn't saw you post
There are such things as atoi. (Note that the master's sample code used strtol also.)
The main reason I used strtol is to make it easier for the OP to identify where his own code can be expanded to take in hexidecimal and octal inputs with just a little extra work.
Mmm.. the man pages for strtol, says that the number needs needs some white spaces and a + or - sign.. is that necessary?, and what about the end of the number, if I don't want to specify one, NULL is ok right? and.. what does the last argument is for?
No, the man pages state that it can have whitespace and a + sign, not that it must. And passing NULL should be fine. The last argument is the base of the number given -- so 2 means "read a binary number", 11 means "read a number in base 11", and so on. If you make it 0, it means "read a number like it's a C constant", so 0whatever is octal and 0xwhatever is hex.
The last argument is the whole reason I even used strtol at all ;) Taking the last argument into consideration you could parse values like 0777 as 511 or 0x000AEF10 as 716560. But the code I posted doesn't automatically just know how to do that. It lazily detects any character and calls the whole parameter a string. So to avoid that you'd have to have it preprocess each variable for octal or hexidecimal numbers.