open read write close

mercuryfrost · 08-20-2009, 01:28 PM

As a progression from the first thread,
which was solved, using fread fscanf fprintf and fclose
(fscanf seg fault)

I'm trying to write the same program,
but in this assignment, I must not use any of the above calls,
but instead use open, read, write, and close.

My code so far compiles fine,
and seems to run, it creates or opens the output file fine,
but doesn't append the input files to it.

I think it's a problem with the read call,
but as I said, I'm new to C!

Any ideas welcome

Code:

#include <stdio.h>
#include <fcntl.h>
#define STR(arg) #arg

#define BUF_SIZE 160

#define BUF_FORMAT "%160[^\n]s"

char buf[BUF_SIZE];
FILE *output, *input, *buffer;									/* declarations*/

int i,j,openstatone,openstattwo;



int main (int argc, char *argv[])
	{
        if ( argc < 2 ) 								/* Error message if no Args entered */
		{
		write(1,  "\n **************** \n Not enough Arguments Supplied\n ****************\nPlease enter an Output file to append to, followed by any input files\n \n",  142);
		
		return 1;
		}	
	else  										/*Output file opened or created */
		{
		openstatone = open(argv[1], O_CREAT, 0777);
		}
	if (openstatone > 0)
		{

		if (argc == 2)									/*If only one Arg entered*/
			{
			write (1, "No input files appended to Output File.\n", 40);			
			return 0;
			}
		else										/* start append section */
			{
			i = argc -2;
			j = 2;
			printf ("i = %d\n", i);
			printf ("j = %d\n", j);
		
	
	
			while (i > 0)								/*Loop through all input files*/
				{
				/*printf ("%s\n", argv[j]);*/					/* Used for Error Checking*/
				openstattwo = open(argv[j], O_RDONLY);

				if (openstattwo > 0)						/*Check fopen worked */
					{
					read (argv[j], buf, 160);
					printf("%s\n", buf);    				/* Used for Error Checking */
					write (argv[1], "%s\n", buf);						
  					close(argv[j]);
					write (1,"SUCCESS! Input File: %s was Successfully appended\n", argv[j], 80);				
					}
				else
					{
					write (1, "FAILURE! Input File: %s Failed to Open or does not exist\n", argv[j], 80);
					}
				j ++;
				i --;
				}
			write (1, "\nFiles Appended Successfully\n\n", 80);				/*Files Appended Successfully*/
			close(argv[1]);			
			return 0;
			}
		}
	else
		{	
		/*write (1, "Output file failed to Open", 80);*/
		return 1;		
		}
	}

tabstop · 08-20-2009, 01:30 PM

If you want to append, why not use O_APPEND?

mercuryfrost · 08-20-2009, 01:34 PM

Well I thought that O_CREAT would create the file and open it. Or just open it if it already exists.

O_APPEND wouldn't open it if the file didn't exist would it?

Well that was my thinking anyway!

tabstop · 08-20-2009, 01:40 PM

You're thinking that these flags are mutually exclusive. They are not. You are supposed to | together the ones you want.

mercuryfrost · 08-20-2009, 02:00 PM

Ah okay,
Changes made.

Still the same problem persists. The input files input isn't being read

I think the problem is with the read statement...

Tidied a bit

Code:

#include <stdio.h>
#include <fcntl.h>
#define STR(arg) #arg

#define BUF_SIZE 160

#define BUF_FORMAT "%160[^\n]s"

char buf[BUF_SIZE];
FILE *output, *input, *buffer;									/* declarations*/

int i,j,outfp,infp,fileread;



int main (int argc, char *argv[])
	{
        if ( argc < 2 ) 								/* Error message if no Args entered */
		{
		write(1,  "\n **************** \n Not enough Arguments Supplied\n ****************\nPlease enter an Output file to append to, followed by any input files\n \n",  142);
		
		return 1;
		}	
	else  										/*Output file opened or created */
		{
		outfp = open(argv[1], O_CREAT | O_APPEND, 0777);
		}
	if (outfp > 0)
		{

		if (argc == 2)									/*If only one Arg entered*/
			{
			write (1, "No input files appended to Output File.\n", 40);			
			return 0;
			}
		else										/* start append section */
			{
			i = argc -2;
			j = 2;
			printf ("i = %d\n", i);
			printf ("j = %d\n", j);
			
			while (i > 0)								/*Loop through all input files*/
				{
				/*printf ("%s\n", argv[j]);*/					/* Used for Error Checking*/
				infp = open(argv[j], O_RDONLY);

				if (infp > 0)						/*Check fopen worked */
					{
					printf ("testing 1\n\n\n");
					
					fileread = read (infp, buf, 160);
					printf("%s\n", buf);    				/* Used for Error Checking */
					write (outfp, buf, 160);						
  					close(infp);
					write (1,"SUCCESS! Input File: %s was Successfully appended\n", argv[j], 80);				
					}
				else
					{				
					write (1, "FAILURE! Input File: %s Failed to Open or does not exist\n", argv[j], 80);
					}
				j ++;
				i --;
				}
			write (1, "\nFiles Appended Successfully\n\n", 80);				/*Files Appended Successfully*/
			close(outfp);			
			return 0;
			}
		}
	else
		{	
		/*write (1, "Output file failed to Open", 80);*/
		return 1;		
		}
	}

nonoob · 08-21-2009, 03:55 PM

What is this stuff:

Code:

read (argv[j], buf, 160);
printf("%s\n", buf);    /* Used for Error Checking */
write (argv[1], "%s\n", buf);

read(), write() and close() expect a file handle... not some string as its first argument.
Also, you can't use formatters.

mercuryfrost · 08-22-2009, 08:09 AM

I think I had already changed that when you had posted.

Did I?

Or is it this you're referring to?

Code:

infp = open(argv[j], O_RDONLY);

If that won't work, any suggestions?

nonoob · 08-23-2009, 05:27 PM

No, the open() looks OK, argument-type-wise.

08-20-2009, 01:30 PM	#2
tabstop and the Hat of Guessing Join Date: Nov 2007 Posts: 8,862	If you want to append, why not use O_APPEND?
tabstop is offline

08-20-2009, 01:34 PM	#3
mercuryfrost Registered User Join Date: Aug 2009 Posts: 18	Well I thought that O_CREAT would create the file and open it. Or just open it if it already exists. O_APPEND wouldn't open it if the file didn't exist would it? Well that was my thinking anyway!
mercuryfrost is offline

08-20-2009, 01:40 PM	#4
tabstop and the Hat of Guessing Join Date: Nov 2007 Posts: 8,862	You're thinking that these flags are mutually exclusive. They are not. You are supposed to \| together the ones you want.
tabstop is offline

08-21-2009, 03:55 PM	#6
nonoob Registered User Join Date: Sep 2008 Location: Toronto, Canada Posts: 525	What is this stuff: Code: read (argv[j], buf, 160); printf("%s\n", buf); /* Used for Error Checking / write (argv[1], "%s\n", buf); read(), write()* and close() expect a file handle... not some string as its first argument. Also, you can't use formatters. Last edited by nonoob; 08-21-2009 at 03:57 PM.
nonoob is offline

08-22-2009, 08:09 AM	#7
mercuryfrost Registered User Join Date: Aug 2009 Posts: 18	I think I had already changed that when you had posted. Did I? Or is it this you're referring to? Code: infp = open(argv[j], O_RDONLY); If that won't work, any suggestions?
mercuryfrost is offline

08-23-2009, 05:27 PM	#8
nonoob Registered User Join Date: Sep 2008 Location: Toronto, Canada Posts: 525	No, the open() looks OK, argument-type-wise.
nonoob is offline

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