Well I’ve done some correcting to my little back scratcher, including two bug fixes and changes to the man page.
/*-
* Copyright (C) 2007
* Terry *. P*****. All rights reserved.
*
* permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
// vim: set noexpandtab ts=8 sw=4 ai :
// vi: set ai nu ts=8 sw=4 :
#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <unistd.h>
struct lnpos {
long nl;
struct lnpos *next;
};
static void readall( FILE *, int );
static void readtop( FILE *, int );
static void readbottom( FILE *, int );
static void usage( void );
/*
* rf - read file to standard out v1.1
*/
int
main( int argc, char *argv[] ) {
char *erptr;
int t_flag = 0, b_flag = 0;
int ch, lncnt;
FILE *fp;
extern char *optarg;
extern int optind;
extern int optopt;
extern int opterr;
extern int optreset;
while ( (ch = getopt(argc, argv, "b:t:")) != -1 ) {
switch (ch) {
case 'b':
b_flag++;
lncnt = strtol(optarg, &erptr, 10);
if ( *erptr || lncnt <= 0 )
errx( 1, "Improper line count -- %s", optarg );
break;
case 't':
t_flag++;
lncnt = strtol(optarg, &erptr, 10);
if ( *erptr || lncnt <= 0 )
errx( 1, "Improper line count -- %s", optarg );
break;
case '?':
default:
usage();
return 1;
}
}
if ( (t_flag < 1) && (b_flag < 1) ) {
fp = fopen( argv[1], "r" );
if ( fp == NULL )
errx( 1, "File can not be opened or"
" does not exist -- %sn", argv[1] );
readall( fp, lncnt );
} else if ( t_flag > 0 ) {
fp = fopen( argv[3], "r" );
if ( fp == NULL )
errx( 1, "File can not be opened or"
" does not exist -- %sn", argv[3] );
readtop( fp, lncnt );
} else if ( b_flag > 0 ) {
fp = fopen( argv[3], "r" );
if ( fp == NULL )
errx( 1, "File can not be opened or"
" does not exist -- %sn", argv[3] );
readbottom( fp, lncnt );
} else {
usage();
/* NOTREACHED */
}
fclose( fp );
return 0;
}
/*
* print out an open file to standard output
*/
static void
readall( FILE *fp, int lncnt ) {
while ( (lncnt = fgetc( fp )) != EOF ) {
printf( "%c", lncnt );
}
}
/* Read n lines from the top of the file.
* note that it was very inspired by the head(1) implementation of BSD
*/
static void
readtop( FILE *fp, int lncnt ) {
char *cp;
size_t error, rlen;
while ( lncnt && (cp = fgetln( fp, &rlen )) != NULL ) {
error = fwrite( cp, sizeof(char), rlen, stdout );
if ( error != rlen )
err( 1, "stdout" );
lncnt--;
}
}
/* Read n lines from the bottom of the file
*/
static void
readbottom( FILE *fp, int lncnt ) {
int hmany = lncnt;
long nlnum = 0;
long where;
struct lnpos *root;
struct lnpos *cur;
root = malloc( sizeof(struct lnpos) );
if ( root == NULL )
err( 1, "can't init the list" );
root->next = 0;
cur = root;
cur->next = malloc( sizeof(struct lnpos) );
if ( cur->next == NULL )
err( 1, "can't add nodes" );
cur = cur->next;
/* read the file, count every 'n' and store them in a new member of
* our linked list.
*/
while ( (lncnt = fgetc( fp )) != EOF ) {
if ( lncnt == 'n' ) {
nlnum++;
cur->nl = ftell( fp );
if ( cur->next != NULL )
cur = cur->next;
cur->next = malloc( sizeof(struct lnpos) );
if ( cur->next == NULL )
err( 1, "can't add nodes" );
cur = cur->next;
}
}
/* rewind our linked-list and seek to b_flag + 1 segments short of the
* end of the list _before_ calling readall. So readall _starts_ from
* the correct fseek offset to print till EOF.
*/
cur = root->next;
hmany++;
while ( hmany < nlnum ) {
cur = cur->next;
nlnum--;
}
where = fseek( fp, cur->nl, SEEK_SET );
if ( where != 0 )
err( 1, "could not seek through the filen" );
readall( fp, lncnt );
}
static void
usage( void ) {
fprintf( stderr, "usage:n rf filen "
"rf [-t number lines from the top] filen "
"rf [ -b number of lines from the bottom ] [ file ]n" );
}
And the manual which writing got me interested in roff, I’ll post when I have time to learn more about it. Basically the problem I had was caused by working on it. Originally under the conditions when 2 + 2 = 5 which is not good, because 2 + 2 is really == 4 !!!! I should never do stuff when I’m like that, but if I don’t try nothing gets done.
