sbase/tail.c

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C
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/* See LICENSE file for copyright and license detaketails. */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "text.h"
#include "util.h"
static void dropinit(FILE *, const char *, long);
static void taketail(FILE *, const char *, long);
int
main(int argc, char *argv[])
{
char *end, c;
long n = 10;
FILE *fp;
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void (*tail)(FILE *, const char *, long) = taketail;
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while((c = getopt(argc, argv, "n:")) != -1)
switch(c) {
case 'n':
n = abs(strtol(optarg, &end, 0));
if(*end != '\0')
eprintf("%s: not a number\n", optarg);
if(optarg[0] == '+')
tail = dropinit;
break;
default:
exit(EXIT_FAILURE);
}
if(optind == argc)
tail(stdin, "<stdin>", n);
else if(optind == argc-1) {
if(!(fp = fopen(argv[optind], "r")))
eprintf("fopen %s:", argv[optind]);
tail(fp, argv[optind], n);
fclose(fp);
}
else
eprintf("usage: %s [-n lines] [file]\n", argv[0]);
return EXIT_SUCCESS;
}
void
dropinit(FILE *fp, const char *str, long n)
{
char buf[BUFSIZ];
long i = 0;
while(i < n && fgets(buf, sizeof buf, fp))
if(buf[strlen(buf)-1] == '\n')
i++;
concat(fp, str, stdout, "<stdout>");
}
void
taketail(FILE *fp, const char *str, long n)
{
char **ring;
long i, j;
size_t *size;
if(!(ring = calloc(n, sizeof *ring)) || !(size = calloc(n, sizeof *size)))
eprintf("calloc:");
for(i = j = 0; afgets(&ring[i], &size[i], fp); i = j = (i+1)%n)
;
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if(ferror(fp))
eprintf("%s: read error:", str);
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do {
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if(ring[j]) {
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fputs(ring[j], stdout);
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free(ring[j]);
}
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} while((j = (j+1)%n) != i);
free(ring);
free(size);
}