sbase/tail.c

/* See LICENSE file for copyright and license details. */
#include <sys/stat.h>

#include <limits.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "text.h"
#include "utf.h"
#include "util.h"

static int    fflag = 0;
static size_t num   = 10;
static char   mode  = 'n';

static void
dropinit(FILE *fp, const char *str)
{
	Rune r;
	char *buf = NULL;
	size_t size = 0, i = 0;
	ssize_t len;

	if (mode == 'n') {
		while (i < num && (len = getline(&buf, &size, fp)) != -1)
			if (len > 0 && buf[len - 1] == '\n')
				i++;
	} else {
		while (i < num && (len = readrune(str, fp, &r)))
			i++;
	}
	free(buf);
	concat(fp, str, stdout, "<stdout>");
}

static void
taketail(FILE *fp, const char *str)
{
	Rune *r = NULL;
	char **ring = NULL;
	size_t i, j, *size = NULL;

	if (mode == 'n') {
		ring = ecalloc(num, sizeof *ring);
		size = ecalloc(num, sizeof *size);

		for (i = j = 0; getline(&ring[i], &size[i], fp) != -1; )
			i = j = (i + 1) % num;
	} else {
		r = ecalloc(num, sizeof *r);

		for (i = j = 0; readrune(str, fp, &r[i]); )
			i = j = (i + 1) % num;
	}
	if (ferror(fp))
		eprintf("%s: read error:", str);

	do {
		if (ring && ring[j]) {
			fputs(ring[j], stdout);
			free(ring[j]);
		} else if (r) {
			writerune("<stdout>", stdout, &r[j]);
		}
	} while ((j = (j + 1) % num) != i);

	free(ring);
	free(size);
	free(r);
}

static void
usage(void)
{
	eprintf("usage: %s [-f] [-c num | -n num] [file ...]\n", argv0);
}

int
main(int argc, char *argv[])
{
	struct stat st1, st2;
	FILE *fp;
	size_t tmpsize;
	int ret = 0, newline, many;
	char *numstr, *tmp;
	void (*tail)(FILE *, const char *) = taketail;

	ARGBEGIN {
	case 'f':
		fflag = 1;
		break;
	case 'c':
	case 'n':
		mode = ARGC();
		numstr = EARGF(usage());
		num = MIN(llabs(estrtonum(numstr, LLONG_MIN + 1, MIN(LLONG_MAX, SIZE_MAX))), SIZE_MAX);
		if (strchr(numstr, '+'))
			tail = dropinit;
		break;
	ARGNUM:
		num = ARGNUMF();
		break;
	default:
		usage();
	} ARGEND;

	if (argc == 0)
		tail(stdin, "<stdin>");
	else {
		if ((many = argc > 1) && fflag)
			usage();
		for (newline = 0; argc > 0; argc--, argv++) {
			if (!(fp = fopen(argv[0], "r"))) {
				weprintf("fopen %s:", argv[0]);
				ret = 1;
				continue;
			}
			if (many)
				printf("%s==> %s <==\n",
				       newline ? "\n" : "", argv[0]);
			if (stat(argv[0], &st1) < 0)
				eprintf("stat %s:", argv[0]);
			if (!(S_ISFIFO(st1.st_mode) || S_ISREG(st1.st_mode)))
				fflag = 0;
			newline = 1;
			tail(fp, argv[0]);

			if (fflag && argc == 1) {
				tmp = NULL;
				tmpsize = 0;
				for(;;) {
					while (getline(&tmp, &tmpsize, fp) != -1) {
						fputs(tmp, stdout);
						fflush(stdout);
					}
					if (ferror(fp))
						eprintf("readline %s:", argv[0]);
					clearerr(fp);
					/* ignore error in case file was removed, we continue
					 * tracking the existing open file descriptor */
					if (!stat(argv[0], &st2)) {
						if (st2.st_size < st1.st_size) {
							fprintf(stderr, "%s: file truncated\n", argv[0]);
							rewind(fp);
						}
						st1 = st2;
					}
					sleep(1);
				}
			}
			fclose(fp);
		}
	}
	return ret;
}