Ad:

C Discussion Thread
Unsolved
Views: 627

Oct 27th, 2009

Write to a file the first word in each line from another file

Expand Post »

Hey

I have a file named filetext.txt with the text:

One word
Two words
Three words
Four words

and the program should read this filetext.txt and output to another file called filecopied.txt this text:

One
Two
Three
Four

I have this so far:

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 *filetext
    FILE *filecopied;
    char text[50];
 
    filetext=fopen("filetext.txt","r");
    filecopied=fopen("filecopied.txt","w");
 
    if ((filetext==NULL) || (filecopied==NULL))
        {
            printf ("A file cannot be opened");
            return 1;
        }
 
       // fgets(text,50,filetext);
        //sscanf("%s ",text);
        sscanf("%s\n",fgets(text,50,filetext));
        //sscanf("%s\n",fgets(text,50,filetext));
        fprintf(filecopied,"%s",text);
        fclose(filecopied);
        fclose(filetext);
        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 *filetext
    FILE *filecopied;
    char text[50];

    filetext=fopen("filetext.txt","r");
    filecopied=fopen("filecopied.txt","w");

    if ((filetext==NULL) || (filecopied==NULL))
        {
            printf ("A file cannot be opened");
            return 1;
        }

       // fgets(text,50,filetext);
        //sscanf("%s ",text);
        sscanf("%s\n",fgets(text,50,filetext));
        //sscanf("%s\n",fgets(text,50,filetext));
        fprintf(filecopied,"%s",text);
        fclose(filecopied);
        fclose(filetext);
        return 0;
}

It doesnt write anything to the file so how can I solve it? Id like to use fgets, fprintf, and sscanf. Thanks.

Last edited by riahc3; Oct 27th, 2009 at 3:04 pm.

Similar Threads

Reading specific line in a file. / Searching in C++
Deleting a line from a file in PHP
how to write and read array record into file?? in Pascal and Delphi
opening a excel from word macro by getting the file name from word at runtime in Visual Basic 4 / 5 / 6
Write int and string to binary file woes in C++

riahc3

Reputation Points: 49

Solved Threads: 1

Posting Whiz

Offline

306 posts
since May 2008

Permalink

Oct 27th, 2009

Re: Write to a file the first word in each line from another file

(Toggle Plain Text)

int main()
{
   FILE *filetext;
   FILE *filecopied;
   char text[50];

   filetext=fopen("filetext.txt","r");
   filecopied=fopen("filecopied.txt","w");

   if ( (filetext==NULL) || (filecopied==NULL) )
   {
      printf ("A file cannot be opened");
      return 1;
   }

   while ( fgets(text, sizeof text, filetext) )
   {
      char first[10];
      if ( sscanf(text, "%9s", first) == 1 )
      {
         fprintf(filecopied, "%s\n", first);
      }
   }
   fclose(filecopied);
   fclose(filetext);
   return 0;
}

Dave Sinkula

Team Colleague

Reputation Points: 2780

Solved Threads: 312

long time no c

Offline

4,790 posts
since Apr 2004

Permalink

Oct 27th, 2009

Re: Write to a file the first word in each line from another file

Quote ...

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>
#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>

It is always good to learn which headers contain which declarations. Including everything under the sun when you use only a small fraction of it is rarely a good idea.

Quote ...

It doesnt write anything to the file so how can I solve it?

Double check the way sscanf() is supposed to be called. What you want are two strings, one for input and one for output:

C Syntax (Toggle Plain Text)
char line[512];
char word[512];
 
while (fgets(line, sizeof line, filetext))
{
    if (sscanf(line, "%511s", word) == 1)
    {
        fprintf(filecopied, "%s\n", word);
    }
}
char line[512];
char word[512];

while (fgets(line, sizeof line, filetext))
{
    if (sscanf(line, "%511s", word) == 1)
    {
        fprintf(filecopied, "%s\n", word);
    }
}

Last edited by Tom Gunn; Oct 27th, 2009 at 3:30 pm. Reason: Saving myself from a nitpick.

Tom Gunn

Reputation Points: 1446

Solved Threads: 135

Practically a Master Poster

Offline

681 posts
since Jun 2009

Permalink

Oct 28th, 2009

-1

Re: Write to a file the first word in each line from another file

I think both of you just limit in another array the amount of chars in a char array when I want it to read/write the first letters then when it detects the first space (" ") and when it detects a "\0", it should just to the next line again the first space and again a "\0" until it reaches EOF...

riahc3

Reputation Points: 49

Solved Threads: 1

Posting Whiz

Offline

306 posts
since May 2008

Permalink

Oct 29th, 2009

Re: Write to a file the first word in each line from another file

Maybe I didnt understand someone correctly...

riahc3

Reputation Points: 49

Solved Threads: 1

Posting Whiz

Offline

306 posts
since May 2008

Permalink

Oct 29th, 2009

Re: Write to a file the first word in each line from another file

Quote ...

Id like to use fgets, fprintf, and sscanf.

Quote ...

I want it to read/write the first letters then when it detects the first space (" ") and when it detects a "\0", it should just to the next line again the first space and again a "\0" until it reaches EOF

These wants do not jive. If you use fgets() alone, you have no choice but to provide a buffer large enough to hold the maximum expected line length. If you use sscanf() to extract a word, you have no choice but to provide a buffer large enough to hold the maximum expected line length because the whole line could be one big word.

You can skip using sscanf() entirely by searching for the first whitespace in the line and save the memory for the second buffer:

C Syntax (Toggle Plain Text)
char line[512];
 
while (fgets(line, sizeof line, filetext))
{
    size_t x = 0;
 
    while (line[x] && !isspace(line[x])) putc(line[x], filecopied);
 
    putc('\n', filecopied);
}
char line[512];

while (fgets(line, sizeof line, filetext))
{
    size_t x = 0;

    while (line[x] && !isspace(line[x])) putc(line[x], filecopied);

    putc('\n', filecopied);
}

The algorithm from the second quote is a viable option, but I would need some convincing to believe that it is a better option than fgets() and sscanf(). Right now I am not sure what it is you want. Dave and I have both given you solutions that match your functional requirement of saving the first word in each line.

Tom Gunn

Reputation Points: 1446

Solved Threads: 135

Practically a Master Poster

Offline

681 posts
since Jun 2009

This thread is more than three months old

No one has posted to this discussion for at least three months. Please let old threads die and do not reply to them unless you feel you have something new and valuable to contribute that absolutely must be added to make the discussion complete. Otherwise, please start a new thread in this forum instead.

Previous Thread in C Forum Timeline: Figuring out redirection of a child process to a file

Next Thread in C Forum Timeline: while condition won't work properly against \n

DaniWeb Message

Cancel Changes

User Name
Password