[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>
#include	<pagsiz.h>
#define	BUFSIZ	BSIZE
#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,BUFSIZ);
					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>BUFSIZ?BUFSIZ:n;
				i = read(0,bin,i);
				if(i<=0) exit(0);
				n -= i;
			}
		else
			lseek(0,n,0);
	}
	while((i=read(0,bin,BUFSIZ))>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
ef7ca5f4 BJ	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	#include <pagsiz.h>
	14	#define BUFSIZ BSIZE
	15	#define LBIN 4097
	16	struct stat statb;
	17	char bin[LBIN];
	18	int errno;
	19
	20	main(argc,argv)
	21	char **argv;
	22	{
	23	long n,di;
	24	int fromend;
	25	register i,j,k;
	26	char *p;
	27	int partial,piped,bylines;
	28	char *arg;
	29	lseek(0,(long)0,1);
	30	piped = errno==ESPIPE;
	31	arg = argv[1];
	32	if(argc<=1 \|\| arg!='-'&&arg!='+') {
	33	arg = "-10l";
	34	argc++;
	35	argv--;
	36	}
	37	fromend = *arg=='-';
	38	arg++;
	39	if(!digit(*arg))
	40	goto errcom;
	41	n = 0;
	42	while(digit(*arg))
	43	n = n10 + arg++ - '0';
	44	if(!fromend&&n>0)
	45	n--;
	46	if(argc>2) {
	47	close(0);
	48	if(open(argv[2],0)!=0) {
	49	write(2,"tail: can't open ",17);
	50	write(2,argv[2],strlen(argv[2]));
	51	write(2,"\n",1);
	52	exit(1);
	53	}
	54	}
	55	bylines = 0;
	56	switch(*arg) {
	57	case 'b':
	58	n <<= 9;
	59	break;
	60	case 'c':
	61	break;
	62	case '\0':
	63	case 'l':
	64	bylines = 1;
65	break;
66	default:
67	goto errcom;
68	}
69	if(fromend)
70	goto keep;
71
72	/seek from beginning /
73
74	if(bylines) {
75	j = 0;
76	while(n-->0) {
77	do {
78	if(j--<=0) {
79	p = bin;
80	j = read(0,p,BUFSIZ);
81	if(j--<=0) exit(0);
82	}
83	} while(*p++ != '\n');
84	}
85	write(1,p,j);
86	} else if(n>0) {
87	if(!piped)
88	fstat(0,&statb);
89	if(piped\|\|(statb.st_mode&S_IFMT)==S_IFCHR)
90	while(n>0) {
91	i = n>BUFSIZ?BUFSIZ:n;
92	i = read(0,bin,i);
93	if(i<=0) exit(0);
94	n -= i;
95	}
96	else
97	lseek(0,n,0);
98	}
99	while((i=read(0,bin,BUFSIZ))>0)
100	write(1,bin,i);
101	exit(0);
102
103	/seek from end/
104
105	keep:
106	if(n<=0) exit(0);
107	if(!piped) {
108	fstat(0,&statb);
109	di = !bylines&&n<LBIN?n:LBIN-1;
110	if(statb.st_size > di)
111	lseek(0,-di,2);
112	}
113	partial = 1;
114	for(;;) {
115	i = 0;
116	do {
117	j = read(0,&bin[i],LBIN-i);
118	if(j<=0)
119	goto brka;
120	i += j;
121	} while(i<LBIN);
122	partial = 0;
123	}
124	brka:
125	if(!bylines) {
126	k =
127	n<=i ? i-n:
128	partial ? 0:
129	n>=LBIN ? i+1:
130	i-n+LBIN;
131	k--;
132	} else {
133	k = i;
134	j = 0;
135	do {
136	do {
137	if(--k<0) {
138	if(partial)
139	goto brkb;
140	k = LBIN -1;
141	}
142	} while(bin[k]!='\n'&&k!=i);
143	} while(j++<n&&k!=i);
144	brkb:
145	if(k==i) do {
146	if(++k>=LBIN)
147	k = 0;
148	} while(bin[k]!='\n'&&k!=i);
149	}
150	if(k<i)
151	write(1,&bin[k+1],i-k-1);
152	else {
153	write(1,&bin[k+1],LBIN-k-1);
154	write(1,bin,i);
155	}
156	exit(0);
157	errcom:
158	write(2,"usage: tail +\b_n[lbc] [file]\n",29);
159	exit(1);
160	}
161
162	digit(c)
163	{
164	return(c>='0'&&c<='9');
165	}