This code works fine when I use a command line argument for fopen()'s parameter, but when I change it to a filename, the program freezes upon compilation. input.txt is definitely there, so I can't figure it out. Thanks.
Code:
#include <stdlib.h>
#include <stdio.h>
#include <ctype.h>
int main(int argc, char **argv)
{
int arr[255]={0};
int i=0;
FILE *text=fopen("input.txt", "r");
while ((i = getchar()) != EOF)
arr[i]++;
fclose(text);
for(i='0'; i<'z'; i++)
{
if(isalnum(i) )
fprintf(stdout, "The number of '%c' is %d\n", i, arr[i]);
}
return 0;
}
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;
}
You can't read from a file opened for append. Try opening it with "a+" instead of "a", that will let you read from the beginning of the file and write to the end.
You really should set your array to zero before you start counting by the way. Your code is only guaranteed to set the first element to zero before it starts counting, the rest may in fact contain undefined values until you set them to zero.
Lastly, you should realize that with two independent processes, they may produce unpredictable results when operating on the same file, i.e. the child process may hit EOF before the parent process finishes appending, or it may not, all depending on which one just happens to get CPU time from the kernel first and when stdio decides to flush buffered output and other random factors.
Last edited by Corona688; 05-01-2009 at 12:28 PM..
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