projects / unix-history / blame
| 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 | } |