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	tail.c - sbase - suckless unix tools
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	---
	tail.c (4355B)
	---
	1 /* See LICENSE file for copyright and license details. */
	2 #include <sys/stat.h>
	3
	4 #include <fcntl.h>
	5 #include <unistd.h>
	6 #include <stdint.h>
	7 #include <stdio.h>
	8 #include <stdlib.h>
	9 #include <string.h>
	10 #include <unistd.h>
	11
	12 #include "utf.h"
	13 #include "util.h"
	14
	15 static char mode = 'n';
	16
	17 static int
	18 dropinit(int fd, const char *fname, size_t count)
	19 {
	20 Rune r;
	21 char buf[BUFSIZ], *p;
	22 ssize_t n;
	23 int nr;
	24
	25 if (count < 2)
	26 goto copy;
	27 count--; /* numbering starts at 1 */
	28 while (count && (n = read(fd, buf, sizeof(buf))) > 0) {
	29 switch (mode) {
	30 case 'n': /* lines */
	31 for (p = buf; count && n > 0; p++, n--) {
	32 if (*p == '\n')
	33 count--;
	34 }
	35 break;
	36 case 'c': /* bytes */
	37 if (count > n) {
	38 count -= n;
	39 } else {
	40 p = buf + count;
	41 n -= count;
	42 count = 0;
	43 }
	44 break;
	45 case 'm': /* runes */
	46 for (p = buf; count && n > 0; p += nr, n -= nr, …
	47 nr = charntorune(&r, p, n);
	48 if (!nr) {
	49 /* we don't have a full rune, mo…
	50 * remaining data to beginning a…
	51 * again */
	52 memmove(buf, p, n);
	53 break;
	54 }
	55 }
	56 break;
	57 }
	58 }
	59 if (count) {
	60 if (n < 0)
	61 weprintf("read %s:", fname);
	62 if (n <= 0)
	63 return n;
	64 }
	65
	66 /* write the rest of the buffer */
	67 if (writeall(1, p, n) < 0)
	68 eprintf("write:");
	69 copy:
	70 switch (concat(fd, fname, 1, "<stdout>")) {
	71 case -1: /* read error */
	72 return -1;
	73 case -2: /* write error */
	74 exit(1);
	75 default:
	76 return 0;
	77 }
	78 }
	79
	80 static int
	81 taketail(int fd, const char *fname, size_t count)
	82 {
	83 static char *buf = NULL;
	84 static size_t size = 0;
	85 char *p;
	86 size_t len = 0, left;
	87 ssize_t n;
	88
	89 if (!count)
	90 return 0;
	91 for (;;) {
	92 if (len + BUFSIZ > size) {
	93 /* make sure we have at least BUFSIZ to read */
	94 size += 2 * BUFSIZ;
	95 buf = erealloc(buf, size);
	96 }
	97 n = read(fd, buf + len, size - len);
	98 if (n < 0) {
	99 weprintf("read %s:", fname);
	100 return -1;
	101 }
	102 if (n == 0)
	103 break;
	104 len += n;
	105 switch (mode) {
	106 case 'n': /* lines */
	107 /* ignore the last character; if it is a newline…
	108 * ends the last line */
	109 for (p = buf + len - 2, left = count; p >= buf; …
	110 if (*p != '\n')
	111 continue;
	112 left--;
	113 if (!left) {
	114 p++;
	115 break;
	116 }
	117 }
	118 break;
	119 case 'c': /* bytes */
	120 p = count < len ? buf + len - count : buf;
	121 break;
	122 case 'm': /* runes */
	123 for (p = buf + len - 1, left = count; p >= buf; …
	124 /* skip utf-8 continuation bytes */
	125 if (UTF8_POINT(*p))
	126 continue;
	127 left--;
	128 if (!left)
	129 break;
	130 }
	131 break;
	132 }
	133 if (p > buf) {
	134 len -= p - buf;
	135 memmove(buf, p, len);
	136 }
	137 }
	138 if (writeall(1, buf, len) < 0)
	139 eprintf("write:");
	140 return 0;
	141 }
	142
	143 static void
	144 usage(void)
	145 {
	146 eprintf("usage: %s [-f] [-c num \| -m num \| -n num \| -num] [file …
	147 }
	148
	149 int
	150 main(int argc, char *argv[])
	151 {
	152 struct stat st1, st2;
	153 int fd;
	154 size_t n = 10;
	155 int fflag = 0, ret = 0, newline = 0, many = 0;
	156 char *numstr;
	157 int (tail)(int, const char , size_t) = taketail;
	158
	159 ARGBEGIN {
	160 case 'f':
	161 fflag = 1;
	162 break;
	163 case 'c':
	164 case 'm':
	165 case 'n':
	166 mode = ARGC();
	167 numstr = EARGF(usage());
	168 n = MIN(llabs(estrtonum(numstr, LLONG_MIN + 1,
	169 MIN(LLONG_MAX, SIZE_MAX))), SIZE…
	170 if (strchr(numstr, '+'))
	171 tail = dropinit;
	172 break;
	173 ARGNUM:
	174 n = ARGNUMF();
	175 break;
	176 default:
	177 usage();
	178 } ARGEND
	179
	180 if (!argc) {
	181 if (tail(0, "<stdin>", n) < 0)
	182 ret = 1;
	183 } else {
	184 if ((many = argc > 1) && fflag)
	185 usage();
	186 for (newline = 0; *argv; argc--, argv++) {
	187 if (!strcmp(*argv, "-")) {
	188 *argv = "<stdin>";
	189 fd = 0;
	190 } else if ((fd = open(*argv, O_RDONLY)) < 0) {
	191 weprintf("open %s:", *argv);
	192 ret = 1;
	193 continue;
	194 }
	195 if (many)
	196 printf("%s==> %s <==\n", newline ? "\n" …
	197 if (fstat(fd, &st1) < 0)
	198 eprintf("fstat %s:", *argv);
	199 if (!(S_ISFIFO(st1.st_mode) \|\| S_ISREG(st1.st_mo…
	200 fflag = 0;
	201 newline = 1;
	202 if (tail(fd, *argv, n) < 0) {
	203 ret = 1;
	204 fflag = 0;
	205 }
	206
	207 if (!fflag) {
	208 if (fd != 0)
	209 close(fd);
	210 continue;
	211 }
	212 for (;;) {
	213 if (concat(fd, *argv, 1, "<stdout>") < 0)
	214 exit(1);
	215 if (fstat(fd, &st2) < 0)
	216 eprintf("fstat %s:", *argv);
	217 if (st2.st_size < st1.st_size) {
	218 fprintf(stderr, "%s: file trunca…
	219 if (lseek(fd, SEEK_SET, 0) < 0)
	220 eprintf("lseek:");
	221 }
	222 st1 = st2;
	223 sleep(1);
	224 }
	225 }
	226 }
	227
	228 return ret;
	229 }