sbase/tail.c

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1.5 KiB
C
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/* See LICENSE file for copyright and license details. */
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#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);
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static void
usage(void)
{
eprintf("usage: %s [-n lines] [file]\n", argv0);
}
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int
main(int argc, char *argv[])
{
long n = 10;
FILE *fp;
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void (*tail)(FILE *, const char *, long) = taketail;
char *lines;
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ARGBEGIN {
case 'n':
lines = EARGF(usage());
n = abs(estrtol(lines, 0));
if(lines[0] == '+')
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tail = dropinit;
break;
default:
usage();
} ARGEND;
if(argc == 0) {
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tail(stdin, "<stdin>", n);
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} else if(argc == 1) {
if(!(fp = fopen(argv[0], "r")))
eprintf("fopen %s:", argv[0]);
tail(fp, argv[0], n);
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fclose(fp);
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} else
usage();
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return 0;
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}
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;
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size_t *size = NULL;
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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);
}