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Reading all pair lines from a file and then putting them in another file

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Join Date: May 2008

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riahc3

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Junior Poster in Training

Reading all pair lines from a file and then putting them in another file

Oct 22nd, 2009

Hey

I have a text file (1.txt) with the lines:

This is line 1
This is line 2
This is line 3
This is line 4
This is line 5

and Im trying to read all the pair lines from that file and write them to another text file called 2.txt which would result in this:

This is line 2
This is line 4

My code works but the problem is at the end it runs into a infinite loop and the result is

This is line 2
This is line 4
This is line 5
This is line 5
This is line 5
This is line 5
This is line 5
This is line 5
This is......

until I manually stop the program. I imagine there is something wrong with my EOF loop and/or the length I set. Also maybe the program doesnt know it should jump to the next line when it reads a /n or something. The variables are in spanish but I THINK they could be understood. If not, Ill translate

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
#include <assert.h>
#include <complex.h>
#include <ctype.h>
#include <errno.h>
#include <fenv.h>
#include <float.h>
#include <inttypes.h>
#include <iso646.h>
#include <limits.h>
#include <locale.h>
#include <math.h>
#include <setjmp.h>
#include <signal.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <wchar.h>
#include <wctype.h>
 
int main()
{
    FILE *archivopar;
    FILE *archivocopiado;
    char texto[50];
    int i=1;
 
    archivopar=fopen("archivopar.txt","r");
    archivocopiado=fopen("archivocopiado.txt","w");
 
 
    if ((archivopar==NULL) || (archivocopiado==NULL))
    {
        printf ("No se puede abrir algun archivo!");
        return 1;
    }
    else
    {
        do{
            fgets(texto,50,archivopar);
            if (i % 2 == 0)
            {
                fprintf(archivocopiado,"%s\n",texto);
            }
            if (archivopar!=EOF)
            {
                i=i+1;
            }
        }while(archivopar!=EOF);
        fclose(archivopar);
        fclose(archivocopiado);
        return 0;
    }
}
#include <assert.h>
#include <complex.h>
#include <ctype.h>
#include <errno.h>
#include <fenv.h>
#include <float.h>
#include <inttypes.h>
#include <iso646.h>
#include <limits.h>
#include <locale.h>
#include <math.h>
#include <setjmp.h>
#include <signal.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <wchar.h>
#include <wctype.h>

int main()
{
    FILE *archivopar;
    FILE *archivocopiado;
    char texto[50];
    int i=1;

    archivopar=fopen("archivopar.txt","r");
    archivocopiado=fopen("archivocopiado.txt","w");


    if ((archivopar==NULL) || (archivocopiado==NULL))
    {
        printf ("No se puede abrir algun archivo!");
        return 1;
    }
    else
    {
        do{
            fgets(texto,50,archivopar);
            if (i % 2 == 0)
            {
                fprintf(archivocopiado,"%s\n",texto);
            }
            if (archivopar!=EOF)
            {
                i=i+1;
            }
        }while(archivopar!=EOF);
        fclose(archivopar);
        fclose(archivocopiado);
        return 0;
    }
}

I know its problably something stupid but I cant figure it out. Thanks for the help.

Last edited by riahc3; Oct 22nd, 2009 at 9:15 pm.

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Join Date: Apr 2004

Posts: 4,393

Reputation: Dave Sinkula has a brilliant future

Solved Threads: 244

Dave Sinkula Dave Sinkula is offline

Offline

long time no c

Oct 22nd, 2009

Change

Help with Code Tags

(Toggle Plain Text)

        do{
            fgets(texto,50,archivopar);
            if (i % 2 == 0)
            {
                fprintf(archivocopiado,"%s\n",texto);
            }
            if (archivopar!=EOF)
            {
                i=i+1;
            }
        }while(archivopar!=EOF);

Help with Code Tags

(Toggle Plain Text)

        while(fgets(texto,sizeof texto,archivopar))
         {
            if (i % 2 == 0)
            {
                fprintf(archivocopiado,"%s\n",texto);
            }
            if (archivopar!=EOF)
            {
                i=i+1;
            }
        }

...more or less.

Last edited by Dave Sinkula; Oct 22nd, 2009 at 10:58 pm.

"One of the methods used by statists to destroy capitalism consists in establishing controls that tie a given industry hand and foot, making it unable to solve its problems, then declaring that freedom has failed and stronger controls are necessary." --Ayn Rand

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Join Date: May 2008

Posts: 82

Reputation: riahc3 is an unknown quantity at this point

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riahc3

Offline

Junior Poster in Training

Oct 22nd, 2009

•

Originally Posted by Dave Sinkula

Change
Help with Code Tags

(Toggle Plain Text)
        do{
            fgets(texto,50,archivopar);
            if (i % 2 == 0)
            {
                fprintf(archivocopiado,"%s\n",texto);
            }
            if (archivopar!=EOF)
            {
                i=i+1;
            }
        }while(archivopar!=EOF);
do{ fgets(texto,50,archivopar); if (i % 2 == 0) { fprintf(archivocopiado,"%s\n",texto); } if (archivopar!=EOF) { i=i+1; } }while(archivopar!=EOF);
to
Help with Code Tags

(Toggle Plain Text)
        while(fgets(texto,sizeof texto,archivopar))
         {
            if (i % 2 == 0)
            {
                fprintf(archivocopiado,"%s\n",texto);
            }
            if (archivopar!=EOF)
            {
                i=i+1;
            }
        }
while(fgets(texto,sizeof texto,archivopar)) { if (i % 2 == 0) { fprintf(archivocopiado,"%s\n",texto); } if (archivopar!=EOF) { i=i+1; } }
...more or less.

Thanks but now its just weird lol....

It copies in the file only the forth line and the seventh line...

•

Join Date: Apr 2004

Posts: 4,393

Reputation: Dave Sinkula has a brilliant future

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Dave Sinkula Dave Sinkula is offline

Offline

long time no c

Oct 23rd, 2009

Yup. It has to do with the incrementing of i. Why would it need to be conditional as you have it?

[edit]I suppose I should have pointed that out earlier. I guess that chunk of my play code didn't tag along with my post. I'd trimmed down unused headers and other things -- I tend to get carried away sometimes.

Last edited by Dave Sinkula; Oct 23rd, 2009 at 12:31 am.

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Join Date: Sep 2009

Posts: 76

Reputation: Gaiety is an unknown quantity at this point

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Gaiety

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Junior Poster in Training

Oct 23rd, 2009

•

Originally Posted by riahc3

Hey

I have a text file (1.txt) with the lines:

This is line 1
This is line 2
This is line 3
This is line 4
This is line 5

and Im trying to read all the pair lines from that file and write them to another text file called 2.txt which would result in this:

This is line 2
This is line 4

My code works but the problem is at the end it runs into a infinite loop and the result is

This is line 2
This is line 4
This is line 5
This is line 5
This is line 5
This is line 5
This is line 5
This is line 5
This is......

until I manually stop the program. I imagine there is something wrong with my EOF loop and/or the length I set. Also maybe the program doesnt know it should jump to the next line when it reads a /n or something. The variables are in spanish but I THINK they could be understood. If not, Ill translate
Help with Code Tags

C Syntax (Toggle Plain Text)
#include <assert.h>
#include <complex.h>
#include <ctype.h>
#include <errno.h>
#include <fenv.h>
#include <float.h>
#include <inttypes.h>
#include <iso646.h>
#include <limits.h>
#include <locale.h>
#include <math.h>
#include <setjmp.h>
#include <signal.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <wchar.h>
#include <wctype.h>
 
int main()
{
    FILE *archivopar;
    FILE *archivocopiado;
    char texto[50];
    int i=1;
 
    archivopar=fopen("archivopar.txt","r");
    archivocopiado=fopen("archivocopiado.txt","w");
 
 
    if ((archivopar==NULL) || (archivocopiado==NULL))
    {
        printf ("No se puede abrir algun archivo!");
        return 1;
    }
    else
    {
        do{
            fgets(texto,50,archivopar);
            if (i % 2 == 0)
            {
                fprintf(archivocopiado,"%s\n",texto);
            }
            if (archivopar!=EOF)
            {
                i=i+1;
            }
        }while(archivopar!=EOF);
        fclose(archivopar);
        fclose(archivocopiado);
        return 0;
    }
}
#include <assert.h> #include <complex.h> #include <ctype.h> #include <errno.h> #include <fenv.h> #include <float.h> #include <inttypes.h> #include <iso646.h> #include <limits.h> #include <locale.h> #include <math.h> #include <setjmp.h> #include <signal.h> #include <stdarg.h> #include <stdbool.h> #include <stddef.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <time.h> #include <wchar.h> #include <wctype.h> int main() { FILE *archivopar; FILE *archivocopiado; char texto[50]; int i=1; archivopar=fopen("archivopar.txt","r"); archivocopiado=fopen("archivocopiado.txt","w"); if ((archivopar==NULL) || (archivocopiado==NULL)) { printf ("No se puede abrir algun archivo!"); return 1; } else { do{ fgets(texto,50,archivopar); if (i % 2 == 0) { fprintf(archivocopiado,"%s\n",texto); } if (archivopar!=EOF) { i=i+1; } }while(archivopar!=EOF); fclose(archivopar); fclose(archivocopiado); return 0; } }
I know its problably something stupid but I cant figure it out. Thanks for the help.

i dont know spanish but i hope u understand this..

the segments

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
  if (archivopar!=EOF)
  if (archivopar!=EOF)

and

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
  while(archivopar!=EOF);
  while(archivopar!=EOF);

are wrong.
archivopar is a FILE pointer and EOF is -1 these will never get equal.
i mean the comparision is wrong.

fgets returns the address of the next line read. And incase if there is no line i.e whenit reaches EOF, it returns the NULL, so you better compare the return address of the fgets to check whether it reached EOF.
NOTE:
fgets read atmost size -1(here 50 -1 = 49) no.of characters including '\n'. and '\n' will be placed in the array when read characters are less than size-1.

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
            char *temp;
 
                temp=fgets(texto,50,archivopar);
                           if (temp!=NULL)
                 while(temp!=NULL);
            char *temp;

                temp=fgets(texto,50,archivopar);
                           if (temp!=NULL)
                 while(temp!=NULL);

it will work with the above changes.

copies only line with even numbers.

Minds are like parachutes - they only work when they are open
Gaiety

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Join Date: May 2008

Posts: 82

Reputation: riahc3 is an unknown quantity at this point

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riahc3

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Junior Poster in Training

Oct 23rd, 2009

Gaiety I did not understand what you mean/said so here is the code translated:

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
#include <assert.h>
#include <complex.h>
#include <ctype.h>
#include <errno.h>
#include <fenv.h>
#include <float.h>
#include <inttypes.h>
#include <iso646.h>
#include <limits.h>
#include <locale.h>
#include <math.h>
#include <setjmp.h>
#include <signal.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <wchar.h>
#include <wctype.h>
 
 
 
 
int main()
{
    FILE *filepairs; //This pointer points to the file that contains the "this is line 1" etc 
    FILE *filecopied; //This pointer points to where the lines will be copied to
    char text[50]; //A string array
    int i=1; //a counter
 
/* Opening the files */
    filepairs=fopen("filepairs.txt","r");
    filecopied=fopen("filecopied.txt","w");
 
 
    if ((filepairs==NULL) || (filecopied==NULL))
    {
        printf ("One of the files cannot be opened!");
        return 1;
    }
    else
    {
        while (fgets(text,sizeof text,filepairs))
        {
            fgets(text,50,filepairs);
            if (i % 2 == 0)
            {
                fprintf(filecopied,"%s\n",text);
            }
            if (filepairs!=NULL)
            {
                i=i+1;
            }
        }
        fclose(filepairs);
        fclose(filecopied);
        return 0;
    }
}
#include <assert.h>
#include <complex.h>
#include <ctype.h>
#include <errno.h>
#include <fenv.h>
#include <float.h>
#include <inttypes.h>
#include <iso646.h>
#include <limits.h>
#include <locale.h>
#include <math.h>
#include <setjmp.h>
#include <signal.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <wchar.h>
#include <wctype.h>




int main()
{
    FILE *filepairs; //This pointer points to the file that contains the "this is line 1" etc 
    FILE *filecopied; //This pointer points to where the lines will be copied to
    char text[50]; //A string array
    int i=1; //a counter

/* Opening the files */
    filepairs=fopen("filepairs.txt","r");
    filecopied=fopen("filecopied.txt","w");


    if ((filepairs==NULL) || (filecopied==NULL))
    {
        printf ("One of the files cannot be opened!");
        return 1;
    }
    else
    {
        while (fgets(text,sizeof text,filepairs))
        {
            fgets(text,50,filepairs);
            if (i % 2 == 0)
            {
                fprintf(filecopied,"%s\n",text);
            }
            if (filepairs!=NULL)
            {
                i=i+1;
            }
        }
        fclose(filepairs);
        fclose(filecopied);
        return 0;
    }
}

I hope this clears it up for everyone. Thanks to everyone for trying to help out

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Join Date: Apr 2004

Posts: 4,393

Reputation: Dave Sinkula has a brilliant future

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Dave Sinkula Dave Sinkula is offline

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long time no c

Oct 23rd, 2009

Just increment i for every line read, right?

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Join Date: Sep 2009

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Reputation: Gaiety is an unknown quantity at this point

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Gaiety

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Junior Poster in Training

Oct 23rd, 2009

•

Gaiety I did not understand what you mean/said so here is the code translated:

try your code with this input:

(i)
filepairs.txt:
This is line 1
This is line 2
This is line 3
This is line 4
This is line 5
This is line 6
This is line 7

you will get out put as :
This is line 4

(ii)
filepairs.txt:
This is line 0
This is line 1
This is line 2
This is line 3
This is line 4
This is line 5
This is line 6

you will get out put as :
This is line 3
This is line 7

Find out whats worng

please explain when the belowstatement becomes false and what is the need of that.

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
 
if (filepairs!=NULL)
 
if (filepairs!=NULL)

•

I hope this clears it up for everyone. Thanks to everyone for trying to help out

the program is not correct yet....!

Minds are like parachutes - they only work when they are open
Gaiety

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