ref: 1018d7a7091fd5e0433f501a3474cdc3fec322cc
dir: /appl/cmd/tail.b/
implement Tail; include "sys.m"; sys: Sys; include "draw.m"; include "bufio.m"; bufmod : Bufio; Iobuf : import bufmod; include "string.m"; str : String; count, anycount, follow : int; file : ref sys->FD; bout : ref Iobuf; BSize : con 8*1024; BEG, END, CHARS, LINES , FWD, REV : con iota; origin := END; units := LINES; dir := FWD; Tail: module { init: fn(nil: ref Draw->Context, argv: list of string); }; init(nil: ref Draw->Context, argv: list of string) { sys = load Sys Sys->PATH; str = load String String->PATH; bufmod = load Bufio Bufio->PATH; seekable : int; bout = bufmod->fopen(sys->fildes(1),bufmod->OWRITE); argv=parse(tl argv); if(dir==REV && (units==CHARS || follow || origin==BEG)) fail("incompatible options"); if(!anycount){ if (dir==REV) count= 16r7fffffff; else count = 10; } if(origin==BEG && units==LINES && count>0) count--; if(len argv > 1) usage(); if(argv == nil || hd argv == "-") { file = sys->fildes(0); seekable = 0; } else { if((file=sys->open(hd argv,sys->OREAD)) == nil ) fatal(hd argv); (nil, stat) := sys->fstat(file); seekable = sys->seek(file,big 0,sys->SEEKSTART) == big 0 && stat.length > big 0; } if(!seekable && origin==END) keep(); else if(!seekable && origin==BEG) skip(); else if(units==CHARS && origin==END){ tseek(big -count, Sys->SEEKEND); copy(); } else if(units==CHARS && origin==BEG){ tseek(big count, Sys->SEEKSTART); copy(); } else if(units==LINES && origin==END) reverse(); else if(units==LINES && origin==BEG) skip(); if(follow){ if(seekable){ d : sys->Dir; d.length=big -1; for(;;){ d=trunc(d.length); copy(); sys->sleep(5000); } }else{ for(;;){ copy(); sys->sleep(5000); } } } exit; } trunc(length : big) : sys->Dir { (nil,d):=sys->fstat(file); if(d.length < length) d.length = tseek(big 0, sys->SEEKSTART); return d; } skip() # read past head of the file to find tail { n : int; buf := array[BSize] of byte; if(units == CHARS) { for( ; count>0; count -=n) { if (count<BSize) n=count; else n=BSize; n = tread(buf, n); if(n == 0) return; } } else { # units == LINES i:=0; n=0; while(count > 0) { n = tread(buf, BSize); if(n == 0) return; for(i=0; i<n && count>0; i++) if(buf[i]==byte '\n') count--; } twrite(buf[i:n]); } copy(); } copy() { buf := array[BSize] of byte; while((n := tread(buf, BSize)) > 0){ twrite(buf[0:n]); } bout.flush(); } keep() # read whole file, keeping the tail { # complexity=length(file)*length(tail). could be linear j, k : int; length:=0; buf : array of byte; tbuf : array of byte; bufsize := 0; for(n:=1; n;) { if(length+BSize > bufsize ) { bufsize += 2*BSize; tbuf = array[bufsize+1] of byte; tbuf[0:]=buf[0:]; buf = tbuf; } for( ; n && length<bufsize; length+=n) n = tread(buf[length:], bufsize-length); if(count >= length) continue; if(units == CHARS) j = length - count; else{ # units == LINES if (int buf[length-1]=='\n') j = length-1; else j=length; for(k=0; j>0; j--) if(int buf[j-1] == '\n') if(++k >= count) break; } length-=j; buf[0:]=buf[j:j+length]; } if(dir == REV) { if(length>0 && buf[length-1]!= byte '\n') buf[length++] = byte '\n'; for(j=length-1 ; j>0; j--) if(buf[j-1] == byte '\n') { twrite(buf[j:length]); if(--count <= 0) return; length = j; } } if(count > 0 && length > 0) twrite(buf[0:length]); bout.flush(); } reverse() # count backward and print tail of file { length := 0; n := 0; buf : array of byte; pos := tseek(big 0, sys->SEEKEND); bufsize := 0; for(first:=1; pos>big 0 && count>0; first=0) { if (pos>big BSize) n = BSize; else n = int pos; pos -= big n; if(length+2*n > bufsize) { bufsize += BSize*((length+2*n-bufsize+BSize-1)/BSize); tbuf := array[bufsize+1] of byte; tbuf[0:] = buf; buf = tbuf; } length += n; abuf := array[length] of byte; abuf[0:] = buf[0:length]; buf[n:] = abuf; tseek(pos, sys->SEEKSTART); if(tread(buf, n) != n) fatal("length error"); if(first && buf[length-1]!= byte '\n') buf[length++] = byte '\n'; for(n=length-1 ; n>0 && count>0; n--) if(buf[n-1] == byte '\n') { count--; if(dir == REV){ twrite(buf[n:length]); bout.flush(); } length = n; } } if(dir == FWD) { if (n==0) tseek(big 0 , sys->SEEKSTART); else tseek(pos+big n+big 1, sys->SEEKSTART); copy(); } else if(count > 0) twrite(buf[0:length]); bout.flush(); } tseek(o : big, p: int) : big { o = sys->seek(file, o, p); if(o == big -1) fatal(""); return o; } tread(buf: array of byte, n: int): int { r := sys->read(file, buf, n); if(r == -1) fatal(""); return r; } twrite(buf:array of byte) { str1:= string buf; if(bout.puts(str1)!=len str1) fatal(""); } fatal(s : string) { sys->fprint(sys->fildes(2), "tail: %s: %r\n", s); exit; } fail(s : string) { sys->fprint(sys->fildes(2), "tail: %s\n", s); exit; } usage() { sys->fprint(sys->fildes(2), "usage: tail [-n N] [-c N] [-f] [-r] [+-N[bc][fr]] [file]\n"); exit; } getnumber(s: string) : int { i:=0; if (len s == 0) return 0; if(s[i]=='-' || s[i]=='+') { if (len s == 1) return 0; i++; } if(!(s[i]>='0' && s[i]<='9')) return 0; if(s[0] == '+') origin = BEG; if(anycount++) fail("excess option"); if (s[0]=='-') s=s[1:]; (count,nil) = str->toint(s,10); if(count < 0){ # protect int args (read, fwrite) fail("too big"); } return 1; } parse(args : list of string) : list of string { for(; args!=nil ; args = tl args ) { hdarg := hd args; if(getnumber(hdarg)) suffix(hdarg); else if(len hdarg > 1 && hdarg[0] == '-') case (hdarg[1]) { 'c' or 'n'=> if (hdarg[1]=='c') units = CHARS; if(len hdarg>2 && getnumber(hdarg[2:])) ; else if(tl args != nil && getnumber(hd tl args)) { args = tl args; } else usage(); 'r' => dir = REV; 'f' => follow++; '-' => args = tl args; } else break; } return args; } suffix(s : string) { i:=0; while(i < len s && str->in(s[i],"0123456789+-")) i++; if (i==len s) return; if (s[i]=='b') if((count*=1024) < 0) fail("too big"); if (s[i]=='c' || s[i]=='b') units = CHARS; if (s[i]=='l' || s[i]=='c' || s[i]=='b') i++; if (i<len s){ case s[i] { 'r'=> dir = REV; return; 'f'=> follow++; return; } } i++; if (i<len s) usage(); }