fopen() - don't know what I'm doing wrong Post: 302312324

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Top Forums Programming fopen() - don't know what I'm doing wrong Post 302312324 by lazypeterson on Thursday 30th of April 2009 11:32:42 PM

05-01-2009

Registered User

Quote:

Originally Posted by frank_rizzo

what do you mean freeze?

the program is waiting for input followed by EOF - ctrl+d on most systems. the text file is not used at all.

you should really check to see if the fopen succeded.

ie:

Code:

    
    FILE *text = NULL;

    text = fopen("input.txt", "r");

    if(text == NULL)
    {
       printf("ERROR: could not open file\n");
       exit(1);
    }

Thanks! I changed some stuff around and got it to work.

I'm having trouble now, again, with writing the output to both the screen and appending the same text file... it successfully appends to it, but not the same output that was outputted to the screen (every occurrence is counted as zero):

Code:

#include <stdlib.h>
#include <stdio.h>
#include <ctype.h>

int main(int argc, char **argv)
{
    pid_t pID = fork();
    
    if (pID == 0) {    //child
      int y[255]={0}, x=0;
       FILE *text=fopen("input.txt", "r");
    
       while ((x = fgetc(text)) != EOF)
           y[x]++;
       fclose(text);
       for(x='0'; x<'z'; x++)
       {
              if(isalnum(x) )
               fprintf(stdout, "The number of '%c' is %d\n", x, y[x]);
       }
       
    }
     else if (pID < 0)            // failed to fork
    {
        exit(1);
    }
        else                                   // parent
    {
      
       int y[255]={0}, x=0;
       FILE *text=fopen("input.txt", "a");
    
       while ((x = fgetc(text)) != EOF)
           y[x]++;
              
       for(x='0'; x<'z'; x++)
       {
              if(isalnum(x) )
               fprintf(text, "The number of '%c' is %d\n", x, y[x]);
       }
     fclose(text);
    }
    
    return 0;
}

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LEARN ABOUT V7

putc

PUTC(3S)																  PUTC(3S)

NAME

       putc, putchar, fputc, putw - put character or word on a stream

SYNOPSIS

       #include <stdio.h>

       int putc(c, stream)
       char c;
       FILE *stream;

       putchar(c)

       fputc(c, stream)
       FILE *stream;

       putw(w, stream)
       FILE *stream;

DESCRIPTION

       Putc appends the character c to the named output stream.  It returns the character written.

       Putchar(c) is defined as putc(c, stdout).

       Fputc behaves like putc, but is a genuine function rather than a macro.	It may be used to save on object text.

       Putw  appends  word (i.e.  int) w to the output stream.	It returns the word written.  Putw neither assumes nor causes special alignment in
       the file.

       The standard stream stdout is normally buffered if and only if the output does not refer to a terminal; this default may be changed by set-
       buf(3).	 The  standard	stream	stderr is by default unbuffered unconditionally, but use of freopen (see fopen(3)) will cause it to become
       buffered; setbuf, again, will set the state to whatever is desired.  When an output stream is unbuffered information appears on the  desti-
       nation  file  or  terminal  as  soon  as  written;  when  it  is buffered many characters are saved up and written as a block.  Fflush (see
       fclose(3)) may be used to force the block out early.

SEE ALSO

       fopen(3), fclose(3), getc(3), puts(3), printf(3), fread(3)

DIAGNOSTICS

       These functions return the constant EOF upon error.  Since this is a good integer, ferror(3) should be used to detect putw errors.

BUGS

       Because it is implemented as a macro, putc treats a stream argument with side effects improperly.  In particular `putc(c,  *f++);'  doesn't
       work sensibly.

																	  PUTC(3S)