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read each line of file

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Ancient Dragon Ancient Dragon is offline

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Re: read each line of file

#11

Feb 14th, 2007

fscanf() does not differentiate between rows. So you will be better off not using that function at all. Instead, I would use fgets() to read one row at a time then parse the string that was read.

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
char line[80];
char *ptr = 0;
int i = 0;
 
while( fgets(line, sizeof(line), f) != NULL)
{
   // clear the array
   memset(v,0,sizeof(v));
   i = 0;
   // extract numbers from line string
   ptr = strtok(line," ");
   while( ptr != NULL)
   {
       // insert into array
       v[i] = atoi(ptr);
      ++i;
      // get next number from the string
      ptr = strtok(NULL, " ");
    }
    // now do something with these numbers
 
}
char line[80];
char *ptr = 0;
int i = 0;

while( fgets(line, sizeof(line), f) != NULL)
{
   // clear the array
   memset(v,0,sizeof(v));
   i = 0;
   // extract numbers from line string
   ptr = strtok(line," ");
   while( ptr != NULL)
   {
       // insert into array
       v[i] = atoi(ptr);
      ++i;
      // get next number from the string
      ptr = strtok(NULL, " ");
    }
    // now do something with these numbers

}

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WaltP

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Posting Sensei

Re: read each line of file

#12

Feb 14th, 2007

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Originally Posted by Ancient Dragon

fscanf() does not differentiate between rows. So you will be better off not using that function at all. Instead, I would use fgets() to read one row at a time then parse the string that was read.
Help with Code Tags

c Syntax (Toggle Plain Text)
char line[80];
char *ptr = 0;
int i = 0;
 
while( fgets(line, sizeof(line), f) != NULL)
{
   // clear the array
   memset(v,0,sizeof(v));
   i = 0;
   // extract numbers from line string
   ptr = strtok(line," ");
   while( ptr != NULL)
   {
       // insert into array
       v[i] = atoi(ptr);
      ++i;
      // get next number from the string
      ptr = strtok(NULL, " ");
    }
    // now do something with these numbers
 
}
char line[80]; char *ptr = 0; int i = 0; while( fgets(line, sizeof(line), f) != NULL) { // clear the array memset(v,0,sizeof(v)); i = 0; // extract numbers from line string ptr = strtok(line," "); while( ptr != NULL) { // insert into array v[i] = atoi(ptr); ++i; // get next number from the string ptr = strtok(NULL, " "); } // now do something with these numbers }

From a purely style issue, I would not use memset() nor strtok(). memset() is not necessary because you should be using only the array values you've loaded so you shouldn't have problems with uninitialized variables. As for strtok() I prefer to parse the values by hand with loops. For example:

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
do
{
    fgets(line, sizeof(line), f) != NULL)
    n = 0;
    // skip leading whitespace
    while (isspace(line[n])) n++;
 
    i = 0;
    do
    {
        // extract numbers from line string
        v[i] = atoi(&line[n]);
 
        // skip to next value
        while (!isspace(line[n])) n++;  // skip over this value
        while ( isspace(line[n])) 
        {
            if (line[n] == '\n')  break;  // isspace() sees \n as whitespace
            n++;  // skip over the spaces
        }
    } while( line[n] != '\n')
do
{
    fgets(line, sizeof(line), f) != NULL)
    n = 0;
    // skip leading whitespace
    while (isspace(line[n])) n++;

    i = 0;
    do
    {
        // extract numbers from line string
        v[i] = atoi(&line[n]);

        // skip to next value
        while (!isspace(line[n])) n++;  // skip over this value
        while ( isspace(line[n])) 
        {
            if (line[n] == '\n')  break;  // isspace() sees \n as whitespace
            n++;  // skip over the spaces
        }
    } while( line[n] != '\n')

I feel I have more control over the input by doing essentially what strtok() does anyway. As I said, purely a personal style issue.

Now, about your code:

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
#include<conio.h>    //// should not use this header, not portable
#include<stdio.h>
main()
{
    clrscr();       //// Not portable.  Also in Standard C you cannot use 
                    //// an executable command before your declarations
    int v[10],v1[10],i=0,j,t,k,number,count=0;
    FILE *f ;
    f = fopen("numbers.inp", "r");   //// please use whitespace
     do
     {
        i++;
        fscanf (f, "%d", &v[i]);    //// please use whitespace for readability
        count++;
     }
     while((number=getc(f))!=EOF);
#include<conio.h>    //// should not use this header, not portable
#include<stdio.h>
main()
{
    clrscr();       //// Not portable.  Also in Standard C you cannot use 
                    //// an executable command before your declarations
    int v[10],v1[10],i=0,j,t,k,number,count=0;
    FILE *f ;
    f = fopen("numbers.inp", "r");   //// please use whitespace
     do
     {
        i++;
        fscanf (f, "%d", &v[i]);    //// please use whitespace for readability
        count++;
     }
     while((number=getc(f))!=EOF);

As ADragon said, fscanf() cannot distinguish end of lines. So you just read all the numbers into your 10-value array and corrupted memory.

One thing you might want to consider for debugging is using printf()'s to display pertinent values as your program executes. Then you would have seen immediately that i was getting too large for your array. You still may not know how to fix it, but at least you know what's happening.

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1) Never do today that which can be put off until tomorrow
2) Tomorrow never comes

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donaldunca donaldunca is offline

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Re: read each line of file

#13

Feb 17th, 2007

•

Originally Posted by Ancient Dragon

fscanf() does not differentiate between rows. So you will be better off not using that function at all. Instead, I would use fgets() to read one row at a time then parse the string that was read.
Help with Code Tags

c Syntax (Toggle Plain Text)
char line[80];
char *ptr = 0;
int i = 0;
 
while( fgets(line, sizeof(line), f) != NULL)
{
   // clear the array
   memset(v,0,sizeof(v));
   i = 0;
   // extract numbers from line string
   ptr = strtok(line," ");
   while( ptr != NULL)
   {
       // insert into array
       v[i] = atoi(ptr);
      ++i;
      // get next number from the string
      ptr = strtok(NULL, " ");
    }
    // now do something with these numbers
 
}
char line[80]; char *ptr = 0; int i = 0; while( fgets(line, sizeof(line), f) != NULL) { // clear the array memset(v,0,sizeof(v)); i = 0; // extract numbers from line string ptr = strtok(line," "); while( ptr != NULL) { // insert into array v[i] = atoi(ptr); ++i; // get next number from the string ptr = strtok(NULL, " "); } // now do something with these numbers }

... but it stop reading at the first line and not jump to second line. Could you help me at this point?
thank you!

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WaltP

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Posting Sensei

Re: read each line of file

#14

Feb 17th, 2007

•

Originally Posted by donaldunca

... but it stop reading at the first line and not jump to second line. Could you help me at this point?
thank you!

Since the only code you posted above is ADragon's code, and his works fine, we have no idea what's wrong with yours.

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1) Never do today that which can be put off until tomorrow
2) Tomorrow never comes

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~s.o.s~

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Re: read each line of file

#15

Feb 17th, 2007

<< mistake >>

Last edited by ~s.o.s~; Feb 17th, 2007 at 12:07 pm.

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John A

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Re: read each line of file

#16

Feb 17th, 2007

•

Originally Posted by donaldunca

... but it stop reading at the first line and not jump to second line. Could you help me at this point?
thank you!

I've experienced problems with fgets() not stopping at each line before. It turns out that the file I was using was from MacOS 9, which used a totally different encoding for newlines, and that was what screwed up fgets().

So if you didn't create the textfile yourself, consider recreating it just to be sure.

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Re: read each line of file

#17

Feb 17th, 2007

Files transferred to MS-Windows from *nix will also have that problem unless the file is run through a translation program. Most FTP programs can correctly translate the file during file transfer operation.

Don't PM me with questions -- you might get a nasty PM in response. If you have a question then post it in one of the forums.