I'm attempting to prompt the user to enter several numbers and, when the user enters a string, the program calculates the sum of those numbers. I'm having difficulty because I want to keep the program as simple as possible without creating other variables to store strings, etc.
int menu(int choice){
int total = 0, values = 0;
char *string = (char*) &values;
switch(choice){
case 1: printf("Enter your values separated by a whitespace: ");
while(string != "compute") {
scanf("%d",&values);
total = total + values;
}
}
return total;
}
I want the user to enter as many numbers as s/he wants (obviously within memory limits), so I have to continually anticipate an int (or other "number"), so what's the most effective way to also anticipate a string?
I know that the following line is a bit sketchy, but why exactly if I want the variable "string" to treat "values" like a string/char type?
char *string = (char*) &values;
To read a string you have to allocate some space for it. You cannot read it into an integer.
To support reading input that could be either an integer or a string, you have to read a string; and then you can try to convert the string to integer.
For example:
char buffer[50];
scanf("%49s", buffer);
if ( 0 == strcmp(buffer, "compute") )
return 0; // they typed "compute"
if ( 0 == sscanf(buffer, "%d", &number) )
break; // they typed something that was not a number
total += number;
When you write like this
int total = 0, values = 0;
char *string = (char*) &values;
You set the pointer string to point to the integer value values so if the user enters a value that is larger than sizeof(values) i.e. sizeof(int), the program will crash.
Instead use a dedicated buffer for the input string
char string[128] = {0};
scanf can be used for input but it is safer to use fgets() to minimize the risk of a buffer overrun:
fgets( string, sizeof(string), stdin );
if you need to hold the individual values entered declare an array of ints e.g.
int values[100];
when the user has enters something check the content of 'string' and see if it
contains compute - it may be enough checking the first char - e.g. if ( string[0] == 'c' ) else convert the string to int and place it in the array of values:
values[i++] = atoi(string);
EDIT:
As McNabb pointed out fgets() adds a \n to the string so if you want to compare the whole string you must take that into account e.g.
if ( !strncmp( "compute", string, strlen("compute") )
{...}
The most efficient method would be to read in a string (use fgets()), then try to decide what it is. If it's an integer, you can use atoi or strtol to convert it. If it's a float, you can use strtod. Otherwise, you can parse the string however you want.
So you'll end up with something like this:
char str[15];
long sum = 0, val;
char* ptr;
while (1)
{
fgets(str, 15, stdin);
if (0 == strcmp(str, "compute"))
{
printf("sum: %d\n", sum);
break;
}
val = strtol(str, &ptr, 10);
// error-check here.
sum += val;
}
Another, simpler option, might be to read integers (using scanf, as in your code above) until end-of-file, then print the sum. That approach has some limitations: you need to give your input through some channel that has a defined EOF, and you can't receive more input after the end of your list of integers. Use a specific value (such as 0) as a sentinel, as Havenard suggested, does not have these drawbacks, but doesn't allow the sentinel value to appear in your list of numbers either.
Not sure why are you trying to compare strings at this point. If you just want to read whitespace separated integers until a non-integer value is entered, let scanf do the work for you:
int menu(int choice){
int total = 0;
int value;
switch(choice){
case 1: printf("Enter your values separated by a whitespace: ");
while(scanf("%d",&value) > 0) {
total += value;
}
}
/* Here, use scanf to get the first non-integer value entered */
return total;
}
Related
Input : [1,3,2,4]
I want to make arr[4] = {1, 3, 2, 4} from this input using scanf(). How can I do this in C language?
It is possible to parse input such as you describe with scanf, but each scanf call will parse up to a maximum number of fields determined by the given format. Thus, to parse an arbitrary number of fields requires an arbitrary number of scanf calls.
In comments, you wrote that
I want to find a method to ignore '[', ']', ',' and only accept integer units.
Taking that as the focus of the question, and therefore ignoring the issues of how you allocate space for the integers to be read when you do not know in advance how many there will be, and assuming that you may not use input functions other than scanf, it seems like you are looking for something along these lines:
int value;
char delim[2] = { 0 };
// Scan and confirm the opening '['
value = 0;
if (scanf("[%n", &value) == EOF) {
// handle end of file or I/O error ...
} else if (value == 0) {
// handle input not starting with a '[' ...
// Note: value == zero because we set it so, and the %n directive went unprocessed
} else {
// if value != 0 then it's because a '[' was scanned and the %n was processed
assert(value == 1);
}
// scan the list items
do {
// One integer plus trailing delimiter, either ',' or ']'
switch(scanf("%d%1[],]", &value, delim)) {
case EOF:
// handle end of file or I/O error (before an integer is read) ...
break;
case 0:
// handle input not starting with an integer ...
// The input may be malformed, but this point will also be reached for an empty list
break;
case 1:
// handle malformed input starting with an integer (which has been scanned) ...
break;
case 2:
// handle valid (to this point) input. The scanned value needs to be stored somewhere ...
break;
default:
// cannot happen
assert(0);
}
// *delim contains the trailing delimiter that was scanned
} while (*delim == ',');
// assuming normal termination of the loop:
assert(*delim == ']');
Points to note:
it is essential to pay attention to the return value of scanf. Failure to do so and to respond appropriately will cause all manner of problems when unexpected input is presented.
the above will accept slightly more general input than you describe, with whitespace (including line terminators) permitted before each integer.
The directive %1[],] attempts to scan a 1-character string whose element is either ] or ,. This is a bit arcane. Also, because the input is scanned as a string, you must be sure to provide space for a string terminator to be written, too.
it would be easier to write a character-by-character parser for your specific format that does not rely on scanf. You could also use scanf to read one character at a time to feed such a parser, but that seems to violate the spirit of the exercise.
While I think that John Bollinger answer is pretty good and complete (even without considering the wonderful %1[[,]), I would go for a more compact and tolerant version like this:
#include <stdio.h>
size_t arr_input(int *arr, size_t max_size)
{
size_t n;
for (n = 0; n < max_size; ++n) {
char c;
int res = scanf("%c%d", &c, arr + n);
if (res != 2
|| (n == 0 && c != '[')
|| (n > 0 && c != ',')
|| (n > 0 && c == ']')) {
break;
}
}
return n;
}
int main(void)
{
char *test_strings[] = { "[1,2,3,4]", "[42]", "[1,1,2,3,5,8]", "[]",
"[10,20,30,40,50,60,70,80,90,100]", "[1,2,3]4" };
size_t test_strings_n = sizeof test_strings / sizeof *test_strings;
char filename[L_tmpnam];
tmpnam(filename);
for (size_t i = 0; i < test_strings_n; ++i) {
freopen(filename, "w+", stdin);
fputs(test_strings[i], stdin);
rewind(stdin);
int arr[9];
size_t num_elem = arr_input(arr, 9);
printf("%zu: %s -> ", i, test_strings[i]);
for (size_t j = 0; j < num_elem; ++j) {
printf("%d ", arr[j]);
}
printf("\n");
fclose(stdin);
}
remove(filename);
return 0;
}
The idea is that you allocate space for the maximum number of integers you accept, then ask the arr_input() function to fill it up to max_size elements.
The check after scanf() tries to cope with incorrect input, but is not very complete. If you trust your input to be correct (don't) you can even make it shorter, by dropping the three || cases.
The most complex thing was to write the test driver with tmp files, strings, reopening and such. Here I'd have loved to have std::istream to just drop a std::stringstream. The fact that the FILE interface doesn't support strings really bugs me.
int arr[4];
for(int i=0;i<4;i++) scanf("%d",&arr[i]);
Are you asking for this? I was little bit confused with your question, if this doesn't solve your query, then don't hesitate to ask again...
use scanf to read a string input from user then parse that input into an integer array
To parse you can use string function "find" to locate the "," and "[]" and then use "atoi" to convert string into integer to fill the destination input array.
Edit: find is a C++ function.
the C function is strchr
How can I split character and variable in 1 line?
Example
INPUT
car1900food2900ram800
OUTPUT
car 1900
food 2900
ram 800
Code
char namax[25];
int hargax;
scanf ("%s%s",&namax,&hargax);
printf ("%s %s",namax,hargax);
If I use code like that, I need double enter or space for make output. How can I split without that?
You should be able to use code like this to read one name and number:
if (scanf("%24[a-zA-Z]%d", namax, &hargax) == 2)
…got name and number OK…
else
…some sort of problem to be reported and handled…
You would need to wrap that in a loop of some sort in order to get three pairs of values. Note that using &namax as an argument to scanf() is technically wrong. The %s, %c and %[…] (scan set) notations all expect a char * argument, but you are passing a char (*)[25] which is quite different. A fortuitous coincidence means you usually get away with the abuse, but it is still not correct and omitting the & is easy (and correct).
You can find details about scan sets etc in the POSIX specification of scanf().
You should consider reading a whole line of input with fgets() or POSIX
getline(), and then processing the resulting string with sscanf(). This makes error reporting and error recovery easier. See also How to use sscanf() in loops.
Since you are asking this question which is actually easy, I presume you are somewhat a beginner in C programming. So instead of trying to split the input itself during the input which seems to be a bit too complicated for someone who's new to C programming, I would suggest something simpler(not efficient when you take memory into account).
Just accept the entire input as a String. Then check the string internally to check for digits and alphabets. I have used ASCII values of them to check. If you find an alphabet followed by a digit, print out the part of string from the last such occurrence till the current point. And while printing this do the same with just a slight tweak with the extracted sub-part, i.e, instead of checking for number followed by letter, check for letter followed by digit, and at that point print as many number of spaces as needed.
just so that you know:
ASCII value of digits (0-9) => 48 to 57
ASCII value of uppercase alphabet (A-Z) => 65 to 90
ASCII value of lowercase alphabets (a-z)
=> 97 to 122
Here is the code:
#include<stdio.h>
#include<string.h>
int main() {
char s[100];
int i, len, j, k = 0, x;
printf("\nenter the string:");
scanf("%s",s);
len = strlen(s);
for(i = 0; i < len; i++){
if(((int)s[i]>=48)&&((int)s[i]<=57)) {
if((((int)s[i+1]>=65)&&((int)s[i+1]<=90))||(((int)s[i+1]>=97)&&((int)s[i+1]<=122))||(i==len-1)) {
for(j = k; j < i+1; j++) {
if(((int)s[j]>=48)&&((int)s[j]<=57)) {
if((((int)s[j-1]>=65)&&((int)s[j-1]<=90))||(((int)s[j-1]>=97)&&((int)s[j-1]<=122))) {
printf("\t");
}
}
printf("%c",s[j]);
}
printf("\n");
k = i + 1;
}
}
}
return(0);
}
the output:
enter the string: car1900food2900ram800
car 1900
food 2900
ram 800
In addition to using a character class to include the characters to read as a string, you can also use the character class to exclude digits which would allow you to scan forward in the string until the next digit is found, taking all characters as your name and then reading the digits as an integer. You can then determine the number of characters consumed so far using the "%n" format specifier and use the resulting number of characters to offset your next read within the line, e.g.
char namax[MAXNM],
*p = buf;
int hargax,
off = 0;
while (sscanf (p, "%24[^0-9]%d%n", namax, &hargax, &off) == 2) {
printf ("%-24s %d\n", namax, hargax);
p += off;
}
Note how the sscanf format string will read up to 24 character that are not digits as namax and then the integer that follows as hargax storing the number of characters consumed in off which is then applied to the pointer p to advance within the buffer in preparation for your next parse with sscanf.
Putting it altogether in a short example, you could do:
#include <stdio.h>
#define MAXNM 25
#define MAXC 1024
int main (void) {
char buf[MAXC] = "";
while (fgets (buf, MAXC, stdin)) {
char namax[MAXNM],
*p = buf;
int hargax,
off = 0;
while (sscanf (p, "%24[^0-9]%d%n", namax, &hargax, &off) == 2) {
printf ("%-24s %d\n", namax, hargax);
p += off;
}
}
}
Example Use/Output
$ echo "car1900food2900ram800" | ./bin/fgetssscanf
car 1900
food 2900
ram 800
I have a txt file that its lines are as follows
[7 chars string][whitespace][5 chars string][whitespace][integer]
I want to use fscanf() to read all these into memory, and I'm confused about what format should I use.
Here's an example of such line:
hello box 94324
Notice the filling whitespaces in each string, apart from the separating whitespace.
Edit: I know about the recommendation to use fgets() first, I cannot use it here.
Edit: here's my code
typedef struct Product {
char* id; //Product ID number. This is the key of the search tree.
char* productName; //Name of the product.
int currentQuantity; //How many items are there in stock, currently.
} Product;
int main()
{
FILE *initial_inventory_file = NULL;
Product product = { NULL, NULL, 0 };
//open file
initial_inventory_file = fopen(INITIAL_INVENTORY_FILE_NAME, "r");
product.id = malloc(sizeof(char) * 10); //- Product ID: 9 digits exactly. (10 for null character)
product.productName = malloc(sizeof(char) * 11); //- Product name: 10 chars exactly.
//go through each line in inital inventory
while (fscanf(initial_inventory_file, "%9c %10c %i", product.id, product.productName, &product.currentQuantity) != EOF)
{
printf("%9c %10c %i\n", product.id, product.productName, product.currentQuantity);
}
//cleanup...
...
}
Here's a file example: (it's actually 10 chars, 9 chars, and int)
022456789 box-large 1234
023356789 cart-small 1234
023456789 box 1234
985477321 dog food 2
987644421 cat food 5555
987654320 snaks 4444
987654321 crate 9999
987654322 pillows 44
Assuming your input file is well-formed, this is the most straightforward version:
char str1[8] = {0};
char str2[6] = {0};
int val;
...
int result = fscanf( input, "%7s %5s %d", str1, str2, &val );
If result is equal to 3, you successfully read all three inputs. If it's less than 3 but not EOF, then you had a matching failure on one or more of your inputs. If it's EOF, you've either hit the end of the file or there was an input error; use feof( input ) to test for EOF at that point.
If you can't guarantee your input file is well-formed (which most of us can't), you're better off reading in the entire line as text and parsing it yourself. You said you can't use fgets, but there's a way to do it with fscanf:
char buffer[128]; // or whatever size you think would be appropriate to read a line at a time
/**
* " %127[^\n]" tells scanf to skip over leading whitespace, then read
* up to 127 characters or until it sees a newline character, whichever
* comes first; the newline character is left in the input stream.
*/
if ( fscanf( input, " %127[^\n]", buffer ) == 1 )
{
// process buffer
}
You can then parse the input buffer using sscanf:
int result = sscanf( buffer, "%7s %5s %d", str1, str2, &val );
if ( result == 3 )
{
// process inputs
}
else
{
// handle input error
}
or by some other method.
EDIT
Edge cases to watch out for:
Missing one or more inputs per line
Malformed input (such as non-numeric text in the integer field)
More than one set of inputs per line
Strings that are longer than 7 or 5 characters
Value too large to store in an int
EDIT 2
The reason most of us don't recommend fscanf is because it sometimes makes error detection and recovery difficult. For example, suppose you have the input records
foo bar 123r4
blurga blah 5678
and you read it with fscanf( input, "%7s %5s %d", str1, str2, &val );. fscanf will read 123 and assign it to val, leaving r4 in the input stream. On the next call, r4 will get assigned to str1, blurga will get assigned to str2, and you'll get a matching failure on blah. Ideally you'd like to reject the whole first record, but by the time you know there's a problem it's too late.
If you read it as a string first, you can parse and check each field, and if any of them are bad, you can reject the whole thing.
Let's assume the input is
<LWS>* <first> <LWS>+ <second> <LWS>+ <integer>
where <LWS> is any whitespace character, including newlines; <first> has one to seven non-whitespace characters; <second> has one to five non-wihitespace characters; <integer> is an optionally signed integer (in hexadecimal if it begins with 0x or 0X, in octal if it begins with 0, or in decimal otherwise); * indicates zero or more of the preceding element; and + indicates one or more of the preceding element.
Let's say you have a structure,
struct record {
char first[8]; /* 7 characters + end-of-string '\0' */
char second[6]; /* 5 characters + end-of-string '\0' */
int number;
};
then you can read the next record from stream in into the structure pointed to by the caller using e.g.
#include <stdlib.h>
#include <stdio.h>
/* Read a record from stream 'in' into *'rec'.
Returns: 0 if success
-1 if invalid parameters
-2 if read error
-3 if non-conforming format
-4 if bug in function
+1 if end of stream (and no data read)
*/
int read_record(FILE *in, struct record *rec)
{
int rc;
/* Invalid parameters? */
if (!in || !rec)
return -1;
/* Try scanning the record. */
rc = fscanf(in, " %7s %5s %d", rec->first, rec->second, &(rec->number));
/* All three fields converted correctly? */
if (rc == 3)
return 0; /* Success! */
/* Only partially converted? */
if (rc > 0)
return -3;
/* Read error? */
if (ferror(in))
return -2;
/* End of input encountered? */
if (feof(in))
return +1;
/* Must be a bug somewhere above. */
return -4;
}
The conversion specifier %7s converts up to seven non-whitespace characters, and %5s up to five; the array (or char pointer) must have room for an additional end-of-string nul byte, '\0', which the scanf() family of functions add automatically.
If you do not specify the length limit, and use %s, the input can overrun the specified buffer. This is a common cause for the common buffer overflow bug.
The return value from the scanf() family of functions is the number of successful conversions (possibly 0), or EOF if an error occurs. Above, we need three conversions to fully scan a record. If we scan just 1 or 2, we have a partial record. Otherwise, we check if a stream error occurred, by checking ferror(). (Note that you want to check ferror() before feof(), because an error condition may also set feof().) If not, we check if the scanning function encountered end-of-stream before anything was converted, using feof().
If none of the above cases were met, then the scanning function returned zero or negative without neither ferror() or feof() returning true. Because the scanning pattern starts with (whitespace and) a conversion specifier, it should never return zero. The only nonpositive return value from the scanf() family of functions is EOF, which should cause feof() to return true. So, if none of the above cases were met, there must be a bug in the code, triggered by some odd corner case in the input.
A program that reads structures from some stream into a dynamically allocated buffer typically implements the following pseudocode:
Set ptr = NULL # Dynamically allocated array
Set num = 0 # Number of entries in array
Set max = 0 # Number of entries allocated for in array
Loop:
If (num >= max):
Calculate new max; num + 1 or larger
Reallocate ptr
If reallocation failed:
Report out of memory
Abort program
End if
End if
rc = read_record(stream, ptr + num)
If rc == 1:
Break out of loop
Else if rc != 0:
Report error (based on rc)
Abort program
End if
End Loop
The issue in your code using the "%9c ..."-format is that %9c does not write the string terminating character. So your string is probably filled with garbage and not terminated at all, which leads to undefined behaviour when printing it out using printf.
If you set the complete content of the strings to 0 before the first scan, it should work as intended. To achieve this, you can use calloc instead of malloc; this will initialise the memory with 0.
Note that the code also has to somehow consumes the newline character, which is solved by an additional fscanf(f,"%*c")-statement (the * indicates that the value is consumed, but not stored to a variable). Will work only if there are no other white spaces between the last digit and the newline character:
int main()
{
FILE *initial_inventory_file = NULL;
Product product = { NULL, NULL, 0 };
//open file
initial_inventory_file = fopen(INITIAL_INVENTORY_FILE_NAME, "r");
product.id = calloc(sizeof(char), 10); //- Product ID: 9 digits exactly. (10 for null character)
product.productName = calloc(sizeof(char), 11); //- Product name: 10 chars exactly.
//go through each line in inital inventory
while (fscanf(initial_inventory_file, "%9c %10c %i", product.id, product.productName, &product.currentQuantity) == 3)
{
printf("%9s %10s %i\n", product.id, product.productName, product.currentQuantity);
fscanf(initial_inventory_file,"%*c");
}
//cleanup...
}
Have you tried the format specifiers?
char seven[8] = {0};
char five[6] = {0};
int myInt = 0;
// loop here
fscanf(fp, "%s %s %d", seven, five, &myInt);
// save to structure / do whatever you want
If you're sure that the formatting and strings are the always fixed length, you could also iterate over input character by character (using something like fgetc() and manually process it. The example above could cause segmentation errors if the string in the file exceeds 5 or 7 characters.
EDIT Manual Scanning Loop:
char seven[8] = {0};
char five[6] = {0};
int myInt = 0;
// loop this part
for (int i = 0; i < 7; i++) {
seven[i] = fgetc(fp);
}
assert(fgetc(fp) == ' '); // consume space (could also use without assert)
for (int i = 0; i < 5; i++) {
five[i] = fgetc(fp);
}
assert(fgetc(fp) == ' '); // consume space (could also use without assert)
fscanf(fp, "%d", &myInt);
I have a while loop that takes a user input until the user says quit but i am not sure how to declare the strings properly. If the user only inputs one word, the second variable will stay the same value from the previous loop.
int main(int argc, char * argv[]){
char user_input[25];
char var1[25], var2[25];
while(strcmp(var1, "quit") != 0){
clear_buffer(user_input);
fgets(user_input, 30, stdin);
sscanf(user_input, "%s %s", var1, var2);
do_stuff(var1, var2);
}
printf("%s", "Done\n");
i am not sure how to declare the strings properly
Strings aren't a type. They're a value pattern, and like other values we don't declare them; we assign them (using strcpy and other functions, in this case). If you say an int stores a multiple of ten, then it ends in 0... If you say an array of char stores a string, then it ends at the first '\0'. Do you see the pattern yet? We can store multiples of ten in different kinds of integer variables, and likewise for strings we can choose different types of character arrays. Similarly for storing numeric values in integer variables, when declaring an array to store a string, you'll want to be sure the array has enough space to store all of the characters for the string plus a '\0' at the end.
If the user only inputs one word, the second variable will stay the same value from the previous loop.
Check the return value of sscanf.
For example, when considering int x = sscanf(user_input, "%s %s", var1, var2); you may want to be sure the 2 arguments you give sscanf are assigned to, in which case you'll be checking that x == 2. If you only care about the first argument being assigned, then you'll be happy when x == 1, too. However, if x <= 0 then you can't trust either var1 or var2
Multiple problems
You never initialize var1 but you use strcmp(), you need to initialize var1 before trying to use strcmp(), if you want to initialize to an empty string just
var1[0] = '\0';
You pass 30 to fgets() but user_input can only hold 25 characters.
Now to why is the program behaving the way it is, you need to check that sscanf() did read both strings, if it doesn't it does not alter the passed parameters.
The scanf() function returns the number of specifiers matched by the input, so if
scanf() returns 0, it means both parameters are not initialized/modified.
scanf() returns 1 one of the parameters is initialized/modified.
When both were initialized/modified, then it will return 2, so checking for that would let you know what is going wrong, and you can print the input string to verify that scanf() was right, and the input was wrong..
Here is a modified version taking comments into account and protecting sscanf arguments:
int main(int argc, char *argv[]) {
char user_input[80];
char var1[25], var2[25];
while (fgets(user_input, (int)(sizeof user_input), stdin)) {
*var2 = '\0';
if (sscanf(user_input, "%24s %24s", var1, var2) > 0) {
if (!strcmp(var1, "quit"))
break;
do_stuff(var1, var2);
}
}
printf("Done\n");
return 0;
}
char user_input[50+1];
char var1[25], var2[25];
while(fgets(user_input, sizeof(user_input), stdin)){
int state = sscanf(user_input, "%24s %24s", var1, var2);
if(state == 1 && strcmp(var1, "quit") == 0)
break;
else if(state == 2)
do_stuff(var1, var2);
}
I have a string that has ints and I'm trying to get all the ints into another array. When sscanf fails to find an int I want the loop to stop. So, I did the following:
int i;
int getout = 0;
for (i = 0; i < bsize && !getout; i++) {
if (!sscanf(startbuffer, "%d", &startarray[i])) {
getout = 1;
}
}
//startbuffer is a string, startarray is an int array.
This results in having all the elements of startarray to be the first char in startbuffer.
sscanf works fine but it doesn't move onto the next int it just stays at the first position.
Any idea what's wrong? Thanks.
The same string pointer is passed each time you call sscanf. If it were to "move" the input, it would have to move all the bytes of the string each time which would be slow for long strings. Furthermore, it would be moving the bytes that weren't scanned.
Instead, you need to implement this yourself by querying it for the number of bytes consumed and the number of values read. Use that information to adjust the pointers yourself.
int nums_now, bytes_now;
int bytes_consumed = 0, nums_read = 0;
while ( ( nums_now =
sscanf( string + bytes_consumed, "%d%n", arr + nums_read, & bytes_now )
) > 0 ) {
bytes_consumed += bytes_now;
nums_read += nums_now;
}
Convert the string to a stream, then you can use fscanf to get the integers.
Try this.
http://www.gnu.org/software/libc/manual/html_node/String-Streams.html
You are correct: sscanf indeed does not "move", because there is nothing to move. If you need to scan a bunch of ints, you can use strtol - it tells you how much it read, so you can feed the next pointer back to the function on the next iteration.
char str[] = "10 21 32 43 54";
char *p = str;
int i;
for (i = 0 ; i != 5 ; i++) {
int n = strtol(p, &p, 10);
printf("%d\n", n);
}
This is the correct behavior of sscanf. sscanf operates on a const char*, not an input stream from a file, so it will not store any information about what it has consumed.
As for the solution, you can use %n in the format string to obtain the number of characters that it has consumed so far (this is defined in C89 standard).
e.g. sscanf("This is a string", "%10s%10s%n", tok1, tok2, &numChar); numChar will contain the number of characters consumed so far. You can use this as an offset to continue scanning the string.
If the string only contains integers that doesn't exceed the maximum value of long type (or long long type), use strtol or strtoll. Beware that long type can be 32-bit or 64-bit, depending on the system.