| 1 | /* |
| 2 | * Copyright (c) 1980 Regents of the University of California. |
| 3 | * All rights reserved. The Berkeley software License Agreement |
| 4 | * specifies the terms and conditions for redistribution. |
| 5 | */ |
| 6 | |
| 7 | #ifndef lint |
| 8 | char copyright[] = |
| 9 | "@(#) Copyright (c) 1980 Regents of the University of California.\n\ |
| 10 | All rights reserved.\n"; |
| 11 | #endif not lint |
| 12 | |
| 13 | #ifndef lint |
| 14 | static char sccsid[] = "@(#)tail.c 5.3 (Berkeley) %G%"; |
| 15 | #endif not lint |
| 16 | |
| 17 | /* tail command |
| 18 | * |
| 19 | * tail where [file] |
| 20 | * where is +/-n[type] |
| 21 | * - means n lines before end |
| 22 | * + means nth line from beginning |
| 23 | * type 'b' means tail n blocks, not lines |
| 24 | * type 'c' means tail n characters |
| 25 | * Type 'r' means in lines in reverse order from end |
| 26 | * (for -r, default is entire buffer ) |
| 27 | * option 'f' means loop endlessly trying to read more |
| 28 | * characters after the end of file, on the assumption |
| 29 | * that the file is growing |
| 30 | */ |
| 31 | |
| 32 | #include <stdio.h> |
| 33 | #include <ctype.h> |
| 34 | #include <sys/types.h> |
| 35 | #include <sys/stat.h> |
| 36 | #include <sys/file.h> |
| 37 | #include <errno.h> |
| 38 | |
| 39 | #define LBIN 32769 |
| 40 | #undef BUFSIZ |
| 41 | #define BUFSIZ 8192 |
| 42 | struct stat statb; |
| 43 | int follow; |
| 44 | int piped; |
| 45 | char bin[LBIN]; |
| 46 | int errno; |
| 47 | |
| 48 | main(argc,argv) |
| 49 | char **argv; |
| 50 | { |
| 51 | long n,di; |
| 52 | register i,j,k; |
| 53 | char *arg; |
| 54 | int partial,bylines,bkwds,fromend,lastnl; |
| 55 | char *p; |
| 56 | |
| 57 | arg = argv[1]; |
| 58 | if(argc<=1 || *arg!='-'&&*arg!='+') { |
| 59 | arg = "-10l"; |
| 60 | argc++; |
| 61 | argv--; |
| 62 | } |
| 63 | fromend = *arg=='-'; |
| 64 | arg++; |
| 65 | if (isdigit(*arg)) { |
| 66 | n = 0; |
| 67 | while(isdigit(*arg)) |
| 68 | n = n*10 + *arg++ - '0'; |
| 69 | } else |
| 70 | n = -1; |
| 71 | if(!fromend&&n>0) |
| 72 | n--; |
| 73 | if(argc>2) { |
| 74 | (void)close(0); |
| 75 | if(open(argv[2],0)!=0) { |
| 76 | perror(argv[2]); |
| 77 | exit(1); |
| 78 | } |
| 79 | } |
| 80 | (void)lseek(0,(off_t)0,L_INCR); |
| 81 | piped = errno==ESPIPE; |
| 82 | bylines = -1; bkwds = 0; |
| 83 | while(*arg) |
| 84 | switch(*arg++) { |
| 85 | |
| 86 | case 'b': |
| 87 | if (n == -1) n = 1; |
| 88 | n <<= 9; |
| 89 | if(bylines!=-1) goto errcom; |
| 90 | bylines=0; |
| 91 | break; |
| 92 | case 'c': |
| 93 | if(bylines!=-1) goto errcom; |
| 94 | bylines=0; |
| 95 | break; |
| 96 | case 'f': |
| 97 | follow = 1; |
| 98 | break; |
| 99 | case 'r': |
| 100 | if(n==-1) n = LBIN; |
| 101 | bkwds = 1; fromend = 1; bylines = 1; |
| 102 | break; |
| 103 | case 'l': |
| 104 | if(bylines!=-1) goto errcom; |
| 105 | bylines = 1; |
| 106 | break; |
| 107 | default: |
| 108 | goto errcom; |
| 109 | } |
| 110 | if (n==-1) n = 10; |
| 111 | if(bylines==-1) bylines = 1; |
| 112 | if(bkwds) follow=0; |
| 113 | if(fromend) |
| 114 | goto keep; |
| 115 | |
| 116 | /*seek from beginning */ |
| 117 | |
| 118 | if(bylines) { |
| 119 | j = 0; |
| 120 | while(n-->0) { |
| 121 | do { |
| 122 | if(j--<=0) { |
| 123 | p = bin; |
| 124 | j = read(0,p,BUFSIZ); |
| 125 | if(j--<=0) |
| 126 | fexit(); |
| 127 | } |
| 128 | } while(*p++ != '\n'); |
| 129 | } |
| 130 | (void)write(1,p,j); |
| 131 | } else if(n>0) { |
| 132 | if(!piped) |
| 133 | (void)fstat(0,&statb); |
| 134 | if(piped||(statb.st_mode&S_IFMT)==S_IFCHR) |
| 135 | while(n>0) { |
| 136 | i = n>BUFSIZ?BUFSIZ:n; |
| 137 | i = read(0,bin,i); |
| 138 | if(i<=0) |
| 139 | fexit(); |
| 140 | n -= i; |
| 141 | } |
| 142 | else |
| 143 | (void)lseek(0,(off_t)n,L_SET); |
| 144 | } |
| 145 | copy: |
| 146 | while((i=read(0,bin,BUFSIZ))>0) |
| 147 | (void)write(1,bin,i); |
| 148 | fexit(); |
| 149 | |
| 150 | /*seek from end*/ |
| 151 | |
| 152 | keep: |
| 153 | if(n <= 0) |
| 154 | fexit(); |
| 155 | if(!piped) { |
| 156 | (void)fstat(0,&statb); |
| 157 | /* If by lines, back up 1 buffer: else back up as needed */ |
| 158 | di = bylines?LBIN-1:n; |
| 159 | if(statb.st_size > di) |
| 160 | (void)lseek(0,(off_t)-di,L_XTND); |
| 161 | if(!bylines) |
| 162 | goto copy; |
| 163 | } |
| 164 | partial = 1; |
| 165 | for(;;) { |
| 166 | i = 0; |
| 167 | do { |
| 168 | j = read(0,&bin[i],LBIN-i); |
| 169 | if(j<=0) |
| 170 | goto brka; |
| 171 | i += j; |
| 172 | } while(i<LBIN); |
| 173 | partial = 0; |
| 174 | } |
| 175 | brka: |
| 176 | if(!bylines) { |
| 177 | k = |
| 178 | n<=i ? i-n: |
| 179 | partial ? 0: |
| 180 | n>=LBIN ? i+1: |
| 181 | i-n+LBIN; |
| 182 | k--; |
| 183 | } else { |
| 184 | if(bkwds && bin[i==0?LBIN-1:i-1]!='\n'){ /* force trailing newline */ |
| 185 | bin[i]='\n'; |
| 186 | if(++i>=LBIN) {i = 0; partial = 0;} |
| 187 | } |
| 188 | k = i; |
| 189 | j = 0; |
| 190 | do { |
| 191 | lastnl = k; |
| 192 | do { |
| 193 | if(--k<0) { |
| 194 | if(partial) { |
| 195 | if(bkwds) |
| 196 | (void)write(1,bin,lastnl+1); |
| 197 | goto brkb; |
| 198 | } |
| 199 | k = LBIN -1; |
| 200 | } |
| 201 | } while(bin[k]!='\n'&&k!=i); |
| 202 | if(bkwds && j>0){ |
| 203 | if(k<lastnl) (void)write(1,&bin[k+1],lastnl-k); |
| 204 | else { |
| 205 | (void)write(1,&bin[k+1],LBIN-k-1); |
| 206 | (void)write(1,bin,lastnl+1); |
| 207 | } |
| 208 | } |
| 209 | } while(j++<n&&k!=i); |
| 210 | brkb: |
| 211 | if(bkwds) exit(0); |
| 212 | if(k==i) do { |
| 213 | if(++k>=LBIN) |
| 214 | k = 0; |
| 215 | } while(bin[k]!='\n'&&k!=i); |
| 216 | } |
| 217 | if(k<i) |
| 218 | (void)write(1,&bin[k+1],i-k-1); |
| 219 | else { |
| 220 | (void)write(1,&bin[k+1],LBIN-k-1); |
| 221 | (void)write(1,bin,i); |
| 222 | } |
| 223 | fexit(); |
| 224 | errcom: |
| 225 | fprintf(stderr, "usage: tail [+\b_[n][lbc][rf]] [file]\n"); |
| 226 | exit(2); |
| 227 | } |
| 228 | |
| 229 | fexit() |
| 230 | { register int n; |
| 231 | if (!follow || piped) exit(0); |
| 232 | for (;;) |
| 233 | { sleep(1); |
| 234 | while ((n = read (0, bin, BUFSIZ)) > 0) |
| 235 | if (write (1, bin, n) < 0) |
| 236 | exit(1); |
| 237 | } |
| 238 | } |