Thread: splitting a string.

Hi gentlemen, I'm trying to split a string that's given in this pattern :
decoder: #(45+HDR)-6, and prints out on the screen the output as:
45
HDR //HDR is a char
6
I tried to use strtok or strtol but didn't benefit, I used while loop that runs on the complete sentence "decoder:#(45+HDR)-6", but it just would be more complex than normal..., eventually I used token's methods.
Code:

Code:

#include <stdio.h>
#include<stdlib.h>
#include<string.h>
int main(void)
{
   char str[80] = "decoder: #(45+HDR)-6";
   const char s[2] = "#";
   char *token;
   
   /* getting the first token */
   token = strtok(str, s);
   
   /* here, I'm walking through other tokens */
   while( token != NULL ) 
   {
      printf( " %s\n", token );
    
      token = strtok(NULL, s);
   }
   return(0);
}

the case here is printing the whole string until arriving to the given "s"-the limit..and I have in this case limits are "#", "+","-"..
this code is working correctly and all good but gives wrong result, I'm not succeeding to print what it should be, so help me please as I'm kinda a new brand C programmer.

You may want to read through this topic since you seem to be working on a similar project. Post#2 might prove interesting.

Jim

thanks.

Sometimes throwing a format string at a problem can be effective.

Code:

   char str[80] = "decoder: #(45+HDR)-6";
   long numbers[2];
   char token[32];

   if ( sscanf(str, "decoder: #(%ld+%3s)-%ld", &numbers[0], token, &numbers[1]) == 3 )
   /* http://linux.die.net/man/3/sscanf */
   { 
      printf("tokenized: %ld %s %ld\n", numbers[0], token, numbers[1]); 
   }

Originally Posted by whiteflags

Sometimes throwing a format string at a problem can be effective.

Code:

   char str[80] = "decoder: #(45+HDR)-6";
   long numbers[2];
   char token[32];

   if ( sscanf(str, "decoder: #(%ld+%3s)-%ld", &numbers[0], token, &numbers[1]) == 3 )
   /* http://linux.die.net/man/3/sscanf */
   { 
      printf("tokenized: %ld %s %ld\n", numbers[0], token, numbers[1]); 
   }

It'll work for a certain situation, what about if the HDR is HDRERT, so how could I change automatically the number which is between "%" and the "s" in the function sscanf-meaning of-"%3s", the number 3 in this statement.

thanks anyway.

It can be done with a general format string, too. Note that the spacing is significant.

Code:

#include <stdio.h>

int main() {
  char line[]        = "decoder: #(45+HDR)-6";
  char line_spaced[] = " decoder : # ( 45 + HDR ) - 6 ";
  char fmt[] = " %31[^: ] : # ( %31[^+- ] %c %31[^) ] ) %c %31s";
  char a[32], b[32], c[32], d[32], op1, op2; // a : # ( b op1 c ) op2 d
  int m;

  *a=*b=*c=*d=0; op1=op2='X';
  m=sscanf(line, fmt, a, b, &op1, c, &op2, d);
  printf("[%d] %s, %s, %c, %s, %c, %s\n", m, a, b, op1, c, op2, d);

  *a=*b=*c=*d=0; op1=op2='X';
  m=sscanf(line_spaced, fmt, a, b, &op1, c, &op2, d);
  printf("[%d] %s, %s, %c, %s, %c, %s\n", m, a, b, op1, c, op2, d);

  return 0;
}

Originally Posted by algorism

It can be done with a general format string, too. Note that the spacing is significant.

Code:

#include <stdio.h>

int main() {
  char line[]        = "decoder: #(45+HDR)-6";
  char line_spaced[] = " decoder : # ( 45 + HDR ) - 6 ";
  char fmt[] = " %31[^: ] : # ( %31[^+- ] %c %31[^) ] ) %c %31s";
  char a[32], b[32], c[32], d[32], op1, op2; // a : # ( b op1 c ) op2 d
  int m;

  *a=*b=*c=*d=0; op1=op2='X';
  m=sscanf(line, fmt, a, b, &op1, c, &op2, d);
  printf("[%d] %s, %s, %c, %s, %c, %s\n", m, a, b, op1, c, op2, d);

  *a=*b=*c=*d=0; op1=op2='X';
  m=sscanf(line_spaced, fmt, a, b, &op1, c, &op2, d);
  printf("[%d] %s, %s, %c, %s, %c, %s\n", m, a, b, op1, c, op2, d);

  return 0;
}

but if I want to print the '45','HDR','6' without the operators and any other things, it will throw out a wrong result, so I guess that's not useful for that statement..

I modified your code, and here it's:

Code:

#include <stdio.h>
#include <string.h>
 
int main() {
  char line[]        = "decoder: #(45+HDR)-6";
  char line_spaced[] = " decoder : # ( 45 + HDR ) - 6";
  char fmt[] = " %31[^: ] : # ( %31[^+- ] %c %31[^) ] ) %c %31s";
  char a[32], b[32], c[32], d[32], op1, op2; // a : # ( b op1 c ) op2 d
  int m;
 
  *a=*b=*c=*d=0; op1=op2='X';
  m=sscanf(a, b,c,d);
  printf("%s, %c, %s, %c, %s\n",a, b,c,d);
  return 0;
}

Originally Posted by whiteflags

There is no especially simple way. You have to try building the string with string functions such as sprintf, strcpy or strncat.
For example, there will be areas in your string where you want %3s, but to write that with sprintf you have to use the string "%%%lds". The %% prints a percent sign, rather than triggering a conversion, the %ld is your magic field width (the 3 in %3s), and finally the s. This all produces %3s.

So you are best served copying as much as you can to the format string variable, then calling sprintf to insert the field width, and copying anything left over.

This is different from printf where you can specify a width using something like %*.s and the arguments are the width, and a string pointer.

Here is an example program with the expected outcome:

Code:

#include <stdio.h>
#include <string.h>
#define FMT_SIZE 80

long BuildFormatString(char *format, long formatSize, long tokenLength);

int main(void)
{
    char format[FMT_SIZE] = "";
    char str[90] = "decoder: #(45+HDR)-6";
    long numbers[2];
    char token[32];
    if (BuildFormatString(format, FMT_SIZE, 3) == FMT_SIZE)
    {
        fprintf(stderr, "format string may be truncated!\n");
        return 0;
    }
    else
    {
        printf("format string: %s\n", format);
    }

    if (sscanf(str, format, &numbers[0], token, &numbers[1]) == 3)
        /* http://linux.die.net/man/3/sscanf */
    {
        printf("tokenized: %ld %s %ld\n", numbers[0], token, numbers[1]);
    }

    return 0;
}

long BuildFormatString(char *format, long formatSize, long tokenLength)
{
    /* Help on functions used:
    http://linux.die.net/man/3/strncpy
    http://linux.die.net/man/3/sprintf
    http://linux.die.net/man/3/strncat
    */
    long length = 0;
    strncpy(format, "decoder: #(%ld+", formatSize - 1);
    length = strlen(format);
    sprintf(&format[length], "%%%lds", tokenLength);
    length = strlen(format);
    strncat(format, ")-%ld", formatSize - length - 1);
    length = strlen(format);
    return length;
}

In my opinion, this is still simpler than other options, but beauty is in the eye of the beholder.

Initially, I'd thank you very much for your concern of..
secondly, this code is still specific for a certain statement, for instance: if I input a string like "decoder: #(45+HDR)-6" it will gives a correct result, but what about if I input "decoder: #(45+HDR)-HERY!" it will stuck over and prints weird things, which it should print '45','HDR','HERY!'.
the pattern of "decoder: #(45+HDR)" isn't gonna be changed and it's stable, but after the "-" I can input whatever things I would like to... string/number/integers..etc, that's what concern me to not using this tokenizer code, thanks.

Originally Posted by migf1

Have you tried the string tokenizer pointed out in post #2?

You may pass it ": #(+)-" as delim, and 4 as maxtoks in order to get back the string tokens "decoder", "45", "HDR" and "6" inside the tokens array. Then it's only a matter of strtoXX()'ing the desired tokens to appropriate variables.

PS. Btw, the tokenizer returns the count of tokens successfully parsed into the tokens array.

Apparently we posted the same comment's content in the same time, read what I've posted recently, it's related to ur comment.

Originally Posted by migf1

Oh now I see what you're saying. You mean you don't know what type one or more tokens should be converted to? If so, then it's a different type of problem (not a "splitting a string" one, I mean).

Huh? I thought on splitting string because we actually extract out specific elements from a string..