Commit | Line | Data |
---|---|---|
15dbf57f BJ |
1 | static char *sccsid = "@(#)tail.c 4.1 (Berkeley) %G%"; |
2 | /* tail command | |
3 | * | |
4 | * tail where [file] | |
5 | * where is +\b_n[type] | |
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 | ||
39 | lseek(0,(long)0,1); | |
40 | piped = errno==ESPIPE; | |
41 | arg = argv[1]; | |
42 | if(argc<=1 || *arg!='-'&&*arg!='+') { | |
43 | arg = "-10l"; | |
44 | argc++; | |
45 | argv--; | |
46 | } | |
47 | fromend = *arg=='-'; | |
48 | arg++; | |
49 | n = 0; | |
50 | while(isdigit(*arg)) | |
51 | n = n*10 + *arg++ - '0'; | |
52 | if(!fromend&&n>0) | |
53 | n--; | |
54 | if(argc>2) { | |
55 | close(0); | |
56 | if(open(argv[2],0)!=0) { | |
57 | perror(argv[2]); | |
58 | exit(1); | |
59 | } | |
60 | } | |
61 | bylines = -1; bkwds = 0; | |
62 | while(*arg) | |
63 | switch(*arg++) { | |
64 | ||
65 | case 'b': | |
66 | n <<= 9; | |
67 | if(bylines!=-1) goto errcom; | |
68 | bylines=0; | |
69 | break; | |
70 | case 'c': | |
71 | if(bylines!=-1) goto errcom; | |
72 | bylines=0; | |
73 | break; | |
74 | case 'f': | |
75 | follow = 1; | |
76 | break; | |
77 | case 'r': | |
78 | if(n==0) n = LBIN; | |
79 | bkwds = 1; fromend = 1; bylines = 1; | |
80 | break; | |
81 | case 'l': | |
82 | if(bylines!=-1) goto errcom; | |
83 | bylines = 1; | |
84 | break; | |
85 | default: | |
86 | goto errcom; | |
87 | } | |
88 | if (n==0) n = 10; | |
89 | if(bylines==-1) bylines = 1; | |
90 | if(bkwds) follow=0; | |
91 | if(fromend) | |
92 | goto keep; | |
93 | ||
94 | /*seek from beginning */ | |
95 | ||
96 | if(bylines) { | |
97 | j = 0; | |
98 | while(n-->0) { | |
99 | do { | |
100 | if(j--<=0) { | |
101 | p = bin; | |
102 | j = read(0,p,BUFSIZ); | |
103 | if(j--<=0) | |
104 | fexit(); | |
105 | } | |
106 | } while(*p++ != '\n'); | |
107 | } | |
108 | write(1,p,j); | |
109 | } else if(n>0) { | |
110 | if(!piped) | |
111 | fstat(0,&statb); | |
112 | if(piped||(statb.st_mode&S_IFMT)==S_IFCHR) | |
113 | while(n>0) { | |
114 | i = n>BUFSIZ?BUFSIZ:n; | |
115 | i = read(0,bin,i); | |
116 | if(i<=0) | |
117 | fexit(); | |
118 | n -= i; | |
119 | } | |
120 | else | |
121 | lseek(0,n,0); | |
122 | } | |
123 | copy: | |
124 | while((i=read(0,bin,BUFSIZ))>0) | |
125 | write(1,bin,i); | |
126 | fexit(); | |
127 | ||
128 | /*seek from end*/ | |
129 | ||
130 | keep: | |
131 | if(n <= 0) | |
132 | fexit(); | |
133 | if(!piped) { | |
134 | fstat(0,&statb); | |
135 | di = !bylines&&n<LBIN?n:LBIN-1; | |
136 | if(statb.st_size > di) | |
137 | lseek(0,-di,2); | |
138 | if(!bylines) | |
139 | goto copy; | |
140 | } | |
141 | partial = 1; | |
142 | for(;;) { | |
143 | i = 0; | |
144 | do { | |
145 | j = read(0,&bin[i],LBIN-i); | |
146 | if(j<=0) | |
147 | goto brka; | |
148 | i += j; | |
149 | } while(i<LBIN); | |
150 | partial = 0; | |
151 | } | |
152 | brka: | |
153 | if(!bylines) { | |
154 | k = | |
155 | n<=i ? i-n: | |
156 | partial ? 0: | |
157 | n>=LBIN ? i+1: | |
158 | i-n+LBIN; | |
159 | k--; | |
160 | } else { | |
161 | if(bkwds && bin[i==0?LBIN-1:i-1]!='\n'){ /* force trailing newline */ | |
162 | bin[i]='\n'; | |
163 | if(++i>=LBIN) {i = 0; partial = 0;} | |
164 | } | |
165 | k = i; | |
166 | j = 0; | |
167 | do { | |
168 | lastnl = k; | |
169 | do { | |
170 | if(--k<0) { | |
171 | if(partial) { | |
172 | if(bkwds) write(1,bin,lastnl+1); | |
173 | goto brkb; | |
174 | } | |
175 | k = LBIN -1; | |
176 | } | |
177 | } while(bin[k]!='\n'&&k!=i); | |
178 | if(bkwds && j>0){ | |
179 | if(k<lastnl) write(1,&bin[k+1],lastnl-k); | |
180 | else { | |
181 | write(1,&bin[k+1],LBIN-k-1); | |
182 | write(1,bin,lastnl+1); | |
183 | } | |
184 | } | |
185 | } while(j++<n&&k!=i); | |
186 | brkb: | |
187 | if(bkwds) exit(0); | |
188 | if(k==i) do { | |
189 | if(++k>=LBIN) | |
190 | k = 0; | |
191 | } while(bin[k]!='\n'&&k!=i); | |
192 | } | |
193 | if(k<i) | |
194 | write(1,&bin[k+1],i-k-1); | |
195 | else { | |
196 | write(1,&bin[k+1],LBIN-k-1); | |
197 | write(1,bin,i); | |
198 | } | |
199 | fexit(); | |
200 | errcom: | |
201 | fprintf(stderr, "usage: tail [+\b_[n][lbc][rf]] [file]\n"); | |
202 | exit(2); | |
203 | } | |
204 | ||
205 | fexit() | |
206 | { register int n; | |
207 | if (!follow || piped) exit(0); | |
208 | for (;;) | |
209 | { sleep(1); | |
210 | while ((n = read (0, bin, BUFSIZ)) > 0) | |
211 | write (1, bin, n); | |
212 | } | |
213 | } |