[unix-history] / usr / src / usr.bin / tail / tail.c

static char *sccsid = "@(#)tail.c	4.4 (Berkeley) %G%";
/* tail command 
 *
 *	tail where [file]
 *	where is +/-n[type]
 *	- means n lines before end
 *	+ means nth line from beginning
 *	type 'b' means tail n blocks, not lines
 *	type 'c' means tail n characters
 *	Type 'r' means in lines in reverse order from end
 *	 (for -r, default is entire buffer )
 *	option 'f' means loop endlessly trying to read more
 *		characters after the end of file, on the  assumption
 *		that the file is growing
*/

#include	<stdio.h>
#include	<ctype.h>
#include	<sys/types.h>
#include	<sys/stat.h>
#include	<errno.h>

#define LBIN 4097
struct	stat	statb;
int	follow;
int	piped;
char bin[LBIN];
int errno;

main(argc,argv)
char **argv;
{
	long n,di;
	register i,j,k;
	char	*arg;
	int partial,bylines,bkwds,fromend,lastnl;
	char *p;

	arg = argv[1];
	if(argc<=1 || *arg!='-'&&*arg!='+') {
		arg = "-10l";
		argc++;
		argv--;
	}
	fromend = *arg=='-';
	arg++;
	if (isdigit(*arg)) {
		n = 0;
		while(isdigit(*arg))
			n = n*10 + *arg++ - '0';
	} else
		n = -1;
	if(!fromend&&n>0)
		n--;
	if(argc>2) {
		close(0);
		if(open(argv[2],0)!=0) {
			perror(argv[2]);
			exit(1);
		}
	}
	lseek(0,(long)0,1);
	piped = errno==ESPIPE;
	bylines = -1; bkwds = 0;
	while(*arg)
	switch(*arg++) {

	case 'b':
		n <<= 9;
		if(bylines!=-1) goto errcom;
		bylines=0;
		break;
	case 'c':
		if(bylines!=-1) goto errcom;
		bylines=0;
		break;
	case 'f':
		follow = 1;
		break;
	case 'r':
		if(n==-1) n = LBIN;
		bkwds = 1; fromend = 1; bylines = 1;
		break;
	case 'l':
		if(bylines!=-1) goto errcom;
		bylines = 1;
		break;
	default:
		goto errcom;
	}
	if (n==-1) n = 10;
	if(bylines==-1) bylines = 1;
	if(bkwds) follow=0;
	if(fromend)
		goto keep;

			/*seek from beginning */

	if(bylines) {
		j = 0;
		while(n-->0) {
			do {
				if(j--<=0) {
					p = bin;
					j = read(0,p,BUFSIZ);
					if(j--<=0)
						fexit();
				}
			} while(*p++ != '\n');
		}
		write(1,p,j);
	} else  if(n>0) {
		if(!piped)
			fstat(0,&statb);
		if(piped||(statb.st_mode&S_IFMT)==S_IFCHR)
			while(n>0) {
				i = n>BUFSIZ?BUFSIZ:n;
				i = read(0,bin,i);
				if(i<=0)
					fexit();
				n -= i;
			}
		else
			lseek(0,n,0);
	}
copy:
	while((i=read(0,bin,BUFSIZ))>0)
		write(1,bin,i);
	fexit();

			/*seek from end*/

keep:
	if(n <= 0)
		fexit();
	if(!piped) {
		fstat(0,&statb);
		di = !bylines&&n<LBIN?n:LBIN-1;
		if(statb.st_size > di)
			lseek(0,-di,2);
		if(!bylines)
			goto copy;
	}
	partial = 1;
	for(;;) {
		i = 0;
		do {
			j = read(0,&bin[i],LBIN-i);
			if(j<=0)
				goto brka;
			i += j;
		} while(i<LBIN);
		partial = 0;
	}
brka:
	if(!bylines) {
		k =
		    n<=i ? i-n:
		    partial ? 0:
		    n>=LBIN ? i+1:
		    i-n+LBIN;
		k--;
	} else {
		if(bkwds && bin[i==0?LBIN-1:i-1]!='\n'){	/* force trailing newline */
			bin[i]='\n';
			if(++i>=LBIN) {i = 0; partial = 0;}
		}
		k = i;
		j = 0;
		do {
			lastnl = k;
			do {
				if(--k<0) {
					if(partial) {
						if(bkwds) write(1,bin,lastnl+1);
						goto brkb;
					}
					k = LBIN -1;
				}
			} while(bin[k]!='\n'&&k!=i);
			if(bkwds && j>0){
				if(k<lastnl) write(1,&bin[k+1],lastnl-k);
				else {
					write(1,&bin[k+1],LBIN-k-1);
					write(1,bin,lastnl+1);
				}
			}
		} while(j++<n&&k!=i);
brkb:
		if(bkwds) exit(0);
		if(k==i) do {
			if(++k>=LBIN)
				k = 0;
		} while(bin[k]!='\n'&&k!=i);
	}
	if(k<i)
		write(1,&bin[k+1],i-k-1);
	else {
		write(1,&bin[k+1],LBIN-k-1);
		write(1,bin,i);
	}
	fexit();
errcom:
	fprintf(stderr, "usage: tail [+\b_[n][lbc][rf]] [file]\n");
	exit(2);
}

fexit()
{	register int n;
	if (!follow || piped) exit(0);
	for (;;)
	{	sleep(1);
		while ((n = read (0, bin, BUFSIZ)) > 0)
			write (1, bin, n);
	}
}
Commit	Line	Data
2b63311e	1	static char *sccsid = "@(#)tail.c 4.4 (Berkeley) %G%";
15dbf57f BJ	2	/* tail command
	3	*
	4	* tail where [file]
bf98c161	5	* where is +/-n[type]
15dbf57f BJ	6	* - means n lines before end
	7	* + means nth line from beginning
	8	* type 'b' means tail n blocks, not lines
	9	* type 'c' means tail n characters
	10	* Type 'r' means in lines in reverse order from end
	11	* (for -r, default is entire buffer )
	12	* option 'f' means loop endlessly trying to read more
	13	* characters after the end of file, on the assumption
	14	* that the file is growing
	15	*/
	16
	17	#include <stdio.h>
	18	#include <ctype.h>
	19	#include <sys/types.h>
	20	#include <sys/stat.h>
	21	#include <errno.h>
	22
	23	#define LBIN 4097
	24	struct stat statb;
	25	int follow;
	26	int piped;
	27	char bin[LBIN];
	28	int errno;
	29
	30	main(argc,argv)
	31	char **argv;
	32	{
	33	long n,di;
	34	register i,j,k;
	35	char *arg;
	36	int partial,bylines,bkwds,fromend,lastnl;
	37	char *p;
	38
15dbf57f BJ	39	arg = argv[1];
	40	if(argc<=1 \|\| arg!='-'&&arg!='+') {
	41	arg = "-10l";
	42	argc++;
	43	argv--;
	44	}
	45	fromend = *arg=='-';
	46	arg++;
2b63311e MK	47	if (isdigit(*arg)) {
	48	n = 0;
	49	while(isdigit(*arg))
	50	n = n10 + arg++ - '0';
	51	} else
	52	n = -1;
15dbf57f BJ	53	if(!fromend&&n>0)
	54	n--;
	55	if(argc>2) {
	56	close(0);
	57	if(open(argv[2],0)!=0) {
	58	perror(argv[2]);
	59	exit(1);
	60	}
	61	}
76c3d437 RC	62	lseek(0,(long)0,1);
76c3d437 RC	63	piped = errno==ESPIPE;
15dbf57f BJ	64	bylines = -1; bkwds = 0;
	65	while(*arg)
	66	switch(*arg++) {
	67
	68	case 'b':
	69	n <<= 9;
	70	if(bylines!=-1) goto errcom;
	71	bylines=0;
	72	break;
	73	case 'c':
	74	if(bylines!=-1) goto errcom;
	75	bylines=0;
	76	break;
	77	case 'f':
	78	follow = 1;
	79	break;
	80	case 'r':
2b63311e	81	if(n==-1) n = LBIN;
15dbf57f BJ	82	bkwds = 1; fromend = 1; bylines = 1;
	83	break;
	84	case 'l':
	85	if(bylines!=-1) goto errcom;
	86	bylines = 1;
	87	break;
	88	default:
	89	goto errcom;
	90	}
2b63311e	91	if (n==-1) n = 10;
15dbf57f BJ	92	if(bylines==-1) bylines = 1;
	93	if(bkwds) follow=0;
	94	if(fromend)
	95	goto keep;
	96
	97	/seek from beginning /
	98
	99	if(bylines) {
	100	j = 0;
	101	while(n-->0) {
	102	do {
	103	if(j--<=0) {
	104	p = bin;
	105	j = read(0,p,BUFSIZ);
	106	if(j--<=0)
	107	fexit();
	108	}
	109	} while(*p++ != '\n');
	110	}
	111	write(1,p,j);
	112	} else if(n>0) {
	113	if(!piped)
	114	fstat(0,&statb);
	115	if(piped\|\|(statb.st_mode&S_IFMT)==S_IFCHR)
	116	while(n>0) {
	117	i = n>BUFSIZ?BUFSIZ:n;
	118	i = read(0,bin,i);
	119	if(i<=0)
	120	fexit();
	121	n -= i;
	122	}
	123	else
	124	lseek(0,n,0);
	125	}
	126	copy:
	127	while((i=read(0,bin,BUFSIZ))>0)
	128	write(1,bin,i);
	129	fexit();
	130
	131	/seek from end/
	132
	133	keep:
	134	if(n <= 0)
	135	fexit();
	136	if(!piped) {
	137	fstat(0,&statb);
	138	di = !bylines&&n<LBIN?n:LBIN-1;
	139	if(statb.st_size > di)
	140	lseek(0,-di,2);
	141	if(!bylines)
	142	goto copy;
	143	}
	144	partial = 1;
	145	for(;;) {
	146	i = 0;
	147	do {
	148	j = read(0,&bin[i],LBIN-i);
	149	if(j<=0)
	150	goto brka;
	151	i += j;
	152	} while(i<LBIN);
	153	partial = 0;
	154	}
	155	brka:
156	if(!bylines) {
157	k =
158	n<=i ? i-n:
159	partial ? 0:
160	n>=LBIN ? i+1:
161	i-n+LBIN;
162	k--;
163	} else {
164	if(bkwds && bin[i==0?LBIN-1:i-1]!='\n'){ /* force trailing newline */
165	bin[i]='\n';
166	if(++i>=LBIN) {i = 0; partial = 0;}
167	}
168	k = i;
169	j = 0;
170	do {
171	lastnl = k;
172	do {
173	if(--k<0) {
174	if(partial) {
175	if(bkwds) write(1,bin,lastnl+1);
176	goto brkb;
177	}
178	k = LBIN -1;
179	}
180	} while(bin[k]!='\n'&&k!=i);
181	if(bkwds && j>0){
182	if(k<lastnl) write(1,&bin[k+1],lastnl-k);
183	else {
184	write(1,&bin[k+1],LBIN-k-1);
185	write(1,bin,lastnl+1);
186	}
187	}
188	} while(j++<n&&k!=i);
189	brkb:
190	if(bkwds) exit(0);
191	if(k==i) do {
192	if(++k>=LBIN)
193	k = 0;
194	} while(bin[k]!='\n'&&k!=i);
195	}
196	if(k<i)
197	write(1,&bin[k+1],i-k-1);
198	else {
199	write(1,&bin[k+1],LBIN-k-1);
200	write(1,bin,i);
201	}
202	fexit();
203	errcom:
204	fprintf(stderr, "usage: tail [+\b_[n][lbc][rf]] [file]\n");
205	exit(2);
206	}
207
208	fexit()
209	{ register int n;
210	if (!follow \|\| piped) exit(0);
211	for (;;)
212	{ sleep(1);
213	while ((n = read (0, bin, BUFSIZ)) > 0)
214	write (1, bin, n);
215	}
216	}