C: Use of setvbuf

[sitko]

Hi,

I'm creating a quick utility which will copy one file into another, but I need it to have the ability to select out certain lines not to copy.

I figured I'd use fread/fwrite but set the buffering size to a line with "setvbuf", here is the code I was going to use as a skeleton for this:

#include <stddef.h>
#include <stdio.h>
#define FAIL 0
#define SUCCESS 1
#define BLOCKSIZE 512
typedef char DATA;
 
int copyfile ( infile, outfile) //I'd add arguments for which strings to exclude
    char *infile, *outfile;
{
    FILE *fp1, *fp2;
    DATA block[BLOCKSIZE];
    int num_read;
 
    if ((fp1 = fopen(infile, "r")) == NULL)
    {
        printf("Error opening file %s for input.\n",infile);
        return FAIL;
    }
 
    if ((fp2 = fopen(outfile, "w")) == NULL)
    {
        printf("Error opening file %s for output.\n",outfile);
        fclose (fp1);
        return FAIL;
    }
 
//code added here from post #2 below
        if (setvbuf(fp1, NULL, _IOLBF, 0) < 0)
    {
                printf("setvbuf error in %s\n",infile);
        return FAIL;
    }
 
    if (setvbuf(fp2, NULL, _IOLBF, 0) < 0)
    {
                printf("setvbuf error in %s\n",outfile);
        return FAIL;
    }
 
    while ((num_read - fread(block, sizeof(DATA), BLOCKSIZE, fp1)) == BLOCKSIZE)
    {
        //Add check for strings to exclude.
        //If (strcmp(line,string)==NULL}
        //{ skip over that line}
        //else {
        fwrite(block, sizeof(DATA), num_read, fp2);
        //}
    }
 
    fwrite(block, sizeof(DATA), num_read, fp2);
    fclose(fp1);
    fclose(fp2);
 
    if (ferror(fp1))
    {
        printf("Error reading file %s\n",infile);
        return FAIL;
    }
    return SUCCESS;
}
 

I want to use setvbuf ( to change the buffering to line buffering, instead of block buffering, but all references I find only cover how to use setvbuf to set the buffering size to NULL..
Here is the syntax for setvbuf:
int setvbuf ( FILE * stream, char * buffer, int mode, size_t size );
mode = (_IOFBF - block buffering, _IOLBF - line buffering, _IONBF - no buffering)

So, what I'm looking for, is how to I use setvbuf to use the _IOLBF, and what changes do I need to make to this code to read LINES instead of BLOCKS.

Thanks,
Sitko.

[sitko]

Hi,

I've since found this code, to set up the setvbuf. Now I just need help converting the BUFFERING to appropriate settings for line buffering...

if (setvbuf(fp1, NULL, _IOLBF, 0) < 0)
    {
        printf("setvbuf error in %s\n",infile);
        return FAIL;
    }
 
    if (setvbuf(fp2, NULL, _IOLBF, 0) < 0)
    {
        printf("setvbuf error in %s\n",outfile);
        return FAIL;
    }
 

Thanks,
Sitko.

[sitko]

Bummer, I found a code snipet that reads lines, instead of blocks. Which uses fgets/fputs.

My boss told me to use fread/fwrite so I got into that train of thought...

The code is virtually the same except for a "#define LINESIZE 100"

and the usage of fgets/fputs:
"while (fgets(line, LINESIZE-1, fp1) != NULL) fputs(line, fp2);"

Thanks,
Sitko.