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reading data from text fies in c

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reading data from text fies in c

Mar 21st, 2007

hi

im asked to read data inputs from a text file in c.

my problem is i dont know to separate the values,

ex. may data contains these:

1.00:2.00:3.00

i would like to assign the values a = 1:00, b = 2.00, c =3.00.

how is it done?

thanks!

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Re: reading data from text fies in c

Mar 21st, 2007

you have a couple options:

1. use strtok() in a loop to extract the individual strings and copy the text into another string array.

2. use a pointer and strchr() to locate each colon then copy the text into another string up to the pointer that was returned by strchr().

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Re: reading data from text fies in c

Mar 22nd, 2007

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
#include <stdio.h>
#include <string.h>
int main ()
{
  char num[] ="1.00:2.00:3.00";
  char *ch;
  char r[100];
  printf ("split \"%s\":\n",num);
  ch = strtok (num,":");
  while (ch != NULL)
  {
    i = 0;
    printf ("%s\n",ch);
    ch = &r[i];
    ch = strtok (NULL, ":");
    i ++;
  }
  return 0;
}
#include <stdio.h>
#include <string.h>
int main ()
{
  char num[] ="1.00:2.00:3.00";
  char *ch;
  char r[100];
  printf ("split \"%s\":\n",num);
  ch = strtok (num,":");
  while (ch != NULL)
  {
    i = 0;
    printf ("%s\n",ch);
    ch = &r[i];
    ch = strtok (NULL, ":");
    i ++;
  }
  return 0;
}

--> here is my strtok code, but it doesn't work.

how can i copy the values of the pointer ch into a char array r? thanks.

Last edited by ~s.o.s~; Mar 22nd, 2007 at 2:22 pm. Reason: Added code tags, learn to use them.

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Re: reading data from text fies in c

Mar 22nd, 2007

Use [search]strcpy[/search] to copy the contents of the string pointed by ch to another string.

Last edited by ~s.o.s~; Mar 22nd, 2007 at 2:29 pm.

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Re: reading data from text fies in c

Mar 23rd, 2007

•

Originally Posted by potato_bum

hi

im asked to read data inputs from a text file in c.

my problem is i dont know to separate the values,

ex. may data contains these:

1.00:2.00:3.00

i would like to assign the values a = 1:00, b = 2.00, c =3.00.

how is it done?

thanks!

This is the code which u want...

/*******************************************/

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
FILE *fpInputFilePtr;
float a[3];
char strTokan[] = {":"};
char *strLineInfo = (char*) calloc(256,1);
char *ptrStrLineInfo = strLineInfo;
int nTmpCnt=0;
fpInputFilePtr = fopen("E:\\Test Projects\\Input.txt","r");
while(fgets(strLineInfo,256,fpInputFilePtr))
{
      strLineInfo[strlen(strLineInfo)-1]='\0';
      while(strlen(strLineInfo)>1)
      {
              strtok(strLineInfo,strTokan);
              a[nTmpCnt]=atof(strLineInfo);
              strLineInfo += strlen(strLineInfo)+1;
      }
      strLineInfo = ptrStrLineInfo;
      memset(strLineInfo,'\0',sizeof(strLineInfo));
}
/******** Do your work here*****/
 
if(fpInputFilePtr)
{
  fclose(fpInputFilePtr);
  fpInputFilePtr=NULL;
}
if(strLineInfo)
{
free(strLineInfo);
strLineInfo=NULL;
}
if(ptrStrLineInfo)
{
free(ptrStrLineInfo);
ptrStrLineInfo=NULL;
}
return 0;
}
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main()
{
FILE *fpInputFilePtr;
float a[3];
char strTokan[] = {":"};
char *strLineInfo = (char*) calloc(256,1);
char *ptrStrLineInfo = strLineInfo;
int nTmpCnt=0;
fpInputFilePtr = fopen("E:\\Test Projects\\Input.txt","r");
while(fgets(strLineInfo,256,fpInputFilePtr))
{
      strLineInfo[strlen(strLineInfo)-1]='\0';
      while(strlen(strLineInfo)>1)
      {
              strtok(strLineInfo,strTokan);
              a[nTmpCnt]=atof(strLineInfo);
              strLineInfo += strlen(strLineInfo)+1;
      }
      strLineInfo = ptrStrLineInfo;
      memset(strLineInfo,'\0',sizeof(strLineInfo));
}
/******** Do your work here*****/

if(fpInputFilePtr)
{
  fclose(fpInputFilePtr);
  fpInputFilePtr=NULL;
}
if(strLineInfo)
{
free(strLineInfo);
strLineInfo=NULL;
}
if(ptrStrLineInfo)
{
free(ptrStrLineInfo);
ptrStrLineInfo=NULL;
}
return 0;
}

/****************************/

If u have any queries feel free to mail to nrk_jegan@yahoo.com

Regards,
Jeganathan Krishnasamy.

Last edited by Ancient Dragon; Mar 23rd, 2007 at 8:40 am. Reason: add missing code tags

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Re: reading data from text fies in c

Mar 23rd, 2007

Sorry, Jeg, but your code doesn't work either. The lines (16-21) using strtok() are incorrect and will only find the first occurence of the colon and no others. Please test out your program to make sure it works before attempting to show someone else how to write a program.

Last edited by Ancient Dragon; Mar 23rd, 2007 at 8:45 am.

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Re: reading data from text fies in c

Mar 26th, 2007

Definitely it'll work.Otherwise i won't put it here.I tested it and working fine.
plz once again check the code by running it or just debug it.I'm incrementing the character pointer.So each time i'm eliminating one ":".
This code is tested for 10 inputs from file.

Last edited by JeganathanK; Mar 26th, 2007 at 1:22 am.

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Re: reading data from text fies in c

Mar 26th, 2007

here is how that loop should have been coded. Your program has a lot of unnecessary and just plain clumbsy code, such as the way it increments strLineInfo

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
while(fgets(strLineInfo,256,fpInputFilePtr))
{
      if( strLineInfo[strlen(strLineInfo)-1] == '\n')
                 strLineInfo[strlen(strLineInfo)-1]='\0';
      ptrStrLineInfo = strtok(strLineInfo,strToken);
      while(ptrStrLineInfo != NULL)
      {
              a[nTmpCnt]=atof(ptrStrLineInfo);
              ++nTmpCnt;
              ptrStrLineInfo = strtok(NULL, strTokan);
      }
}
while(fgets(strLineInfo,256,fpInputFilePtr))
{
      if( strLineInfo[strlen(strLineInfo)-1] == '\n')
                 strLineInfo[strlen(strLineInfo)-1]='\0';
      ptrStrLineInfo = strtok(strLineInfo,strToken);
      while(ptrStrLineInfo != NULL)
      {
              a[nTmpCnt]=atof(ptrStrLineInfo);
              ++nTmpCnt;
              ptrStrLineInfo = strtok(NULL, strTokan);
      }
}

>>memset(strLineInfo,'\0',sizeof(strLineInfo));
Since strLineInfo is a pointer the sizeof operator will always return the size of a pointer, which is 4 on most 32-bit compilers. So that memset line is pretty useless.