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

/* tail command 
 *
 *	tail where [file]
 *	where is +\b_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
*/
#include	<sys/types.h>
#include	<sys/stat.h>
#include	<errno.h>
#define LBIN 4097
struct	stat	statb;
char bin[LBIN];
int errno;

main(argc,argv)
char **argv;
{
	long n,di;
	int fromend;
	register i,j,k;
	char *p;
	int partial,piped,bylines;
	char *arg;
	lseek(0,(long)0,1);
	piped = errno==ESPIPE;
	arg = argv[1];
	if(argc<=1 || *arg!='-'&&*arg!='+') {
		arg = "-10l";
		argc++;
		argv--;
	}
	fromend = *arg=='-';
	arg++;
	if(!digit(*arg))
		goto errcom;
	n = 0;
	while(digit(*arg))
		n = n*10 + *arg++ - '0';
	if(!fromend&&n>0)
		n--;
	if(argc>2) {
		close(0);
		if(open(argv[2],0)!=0) {
			write(2,"tail: can't open ",17);
			write(2,argv[2],strlen(argv[2]));
			write(2,"\n",1);
			exit(1);
		}
	}
	bylines = 0;
	switch(*arg) {
	case 'b':
		n <<= 9;
		break;
	case 'c':
		break;
	case '\0':
	case 'l':
		bylines = 1;
		break;
	default:
		goto errcom;
	}
	if(fromend)
		goto keep;

			/*seek from beginning */

	if(bylines) {
		j = 0;
		while(n-->0) {
			do {
				if(j--<=0) {
					p = bin;
					j = read(0,p,512);
					if(j--<=0) exit(0);
				}
			} 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>512?512:n;
				i = read(0,bin,i);
				if(i<=0) exit(0);
				n -= i;
			}
		else
			lseek(0,n,0);
	}
	while((i=read(0,bin,512))>0)
		write(1,bin,i);
	exit(0);

			/*seek from end*/

keep:
	if(n<=0) exit(0);
	if(!piped) {
		fstat(0,&statb);
		di = !bylines&&n<LBIN?n:LBIN-1;
		if(statb.st_size > di)
			lseek(0,-di,2);
	}
	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 {
		k = i;
		j = 0;
		do {
			do {
				if(--k<0) {
					if(partial)
						goto brkb;
					k = LBIN -1;
				}
			} while(bin[k]!='\n'&&k!=i);
		} while(j++<n&&k!=i);
brkb:
		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);
	}
	exit(0);
errcom:
	write(2,"usage: tail +\b_n[lbc] [file]\n",29);
	exit(1);
}

digit(c)
{
	return(c>='0'&&c<='9');
}
Commit	Line	Data
3b600ead TL	1	/* tail command
	2	*
	3	* tail where [file]
	4	* where is +\b_n[type]
	5	* - means n lines before end
	6	* + means nth line from beginning
	7	* type 'b' means tail n blocks, not lines
	8	* type 'c' means tail n characters
	9	*/
	10	#include <sys/types.h>
	11	#include <sys/stat.h>
	12	#include <errno.h>
	13	#define LBIN 4097
	14	struct stat statb;
	15	char bin[LBIN];
	16	int errno;
	17
	18	main(argc,argv)
	19	char **argv;
	20	{
	21	long n,di;
	22	int fromend;
	23	register i,j,k;
	24	char *p;
	25	int partial,piped,bylines;
	26	char *arg;
	27	lseek(0,(long)0,1);
	28	piped = errno==ESPIPE;
	29	arg = argv[1];
	30	if(argc<=1 \|\| arg!='-'&&arg!='+') {
	31	arg = "-10l";
	32	argc++;
	33	argv--;
	34	}
	35	fromend = *arg=='-';
	36	arg++;
	37	if(!digit(*arg))
	38	goto errcom;
	39	n = 0;
	40	while(digit(*arg))
	41	n = n10 + arg++ - '0';
	42	if(!fromend&&n>0)
	43	n--;
	44	if(argc>2) {
	45	close(0);
	46	if(open(argv[2],0)!=0) {
	47	write(2,"tail: can't open ",17);
	48	write(2,argv[2],strlen(argv[2]));
	49	write(2,"\n",1);
	50	exit(1);
	51	}
	52	}
	53	bylines = 0;
	54	switch(*arg) {
	55	case 'b':
	56	n <<= 9;
	57	break;
	58	case 'c':
	59	break;
	60	case '\0':
	61	case 'l':
	62	bylines = 1;
	63	break;
	64	default:
65	goto errcom;
66	}
67	if(fromend)
68	goto keep;
69
70	/seek from beginning /
71
72	if(bylines) {
73	j = 0;
74	while(n-->0) {
75	do {
76	if(j--<=0) {
77	p = bin;
78	j = read(0,p,512);
79	if(j--<=0) exit(0);
80	}
81	} while(*p++ != '\n');
82	}
83	write(1,p,j);
84	} else if(n>0) {
85	if(!piped)
86	fstat(0,&statb);
87	if(piped\|\|(statb.st_mode&S_IFMT)==S_IFCHR)
88	while(n>0) {
89	i = n>512?512:n;
90	i = read(0,bin,i);
91	if(i<=0) exit(0);
92	n -= i;
93	}
94	else
95	lseek(0,n,0);
96	}
97	while((i=read(0,bin,512))>0)
98	write(1,bin,i);
99	exit(0);
100
101	/seek from end/
102
103	keep:
104	if(n<=0) exit(0);
105	if(!piped) {
106	fstat(0,&statb);
107	di = !bylines&&n<LBIN?n:LBIN-1;
108	if(statb.st_size > di)
109	lseek(0,-di,2);
110	}
111	partial = 1;
112	for(;;) {
113	i = 0;
114	do {
115	j = read(0,&bin[i],LBIN-i);
116	if(j<=0)
117	goto brka;
118	i += j;
119	} while(i<LBIN);
120	partial = 0;
121	}
122	brka:
123	if(!bylines) {
124	k =
125	n<=i ? i-n:
126	partial ? 0:
127	n>=LBIN ? i+1:
128	i-n+LBIN;
129	k--;
130	} else {
131	k = i;
132	j = 0;
133	do {
134	do {
135	if(--k<0) {
136	if(partial)
137	goto brkb;
138	k = LBIN -1;
139	}
140	} while(bin[k]!='\n'&&k!=i);
141	} while(j++<n&&k!=i);
142	brkb:
143	if(k==i) do {
144	if(++k>=LBIN)
145	k = 0;
146	} while(bin[k]!='\n'&&k!=i);
147	}
148	if(k<i)
149	write(1,&bin[k+1],i-k-1);
150	else {
151	write(1,&bin[k+1],LBIN-k-1);
152	write(1,bin,i);
153	}
154	exit(0);
155	errcom:
156	write(2,"usage: tail +\b_n[lbc] [file]\n",29);
157	exit(1);
158	}
159
160	digit(c)
161	{
162	return(c>='0'&&c<='9');
163	}