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#include <u.h>
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#include <libc.h>
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#define U(x) (x<<6)
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#define G(x) (x<<3)
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#define O(x) (x)
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#define A(x) (U(x)|G(x)|O(x))
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#define DMRWE (DMREAD|DMWRITE|DMEXEC)
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int parsemode(char *, ulong *, ulong *);
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void
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main(int argc, char *argv[])
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{
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	int i;
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	Dir *dir, ndir;
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	ulong mode, mask;
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	char *p;
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	if(argc < 3){
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		fprint(2, "usage: chmod 0777 file ... or chmod [who]op[rwxalt] file ...\n");
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		exits("usage");
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	}
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	mode = strtol(argv[1], &p, 8);
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	if(*p == 0)
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		mask = A(DMRWE);
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	else if(!parsemode(argv[1], &mask, &mode)){
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		fprint(2, "chmod: bad mode: %s\n", argv[1]);
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		exits("mode");
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	}
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	nulldir(&ndir);
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	for(i=2; i<argc; i++){
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		dir = dirstat(argv[i]);
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		if(dir == nil){
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			fprint(2, "chmod: can't stat %s: %r\n", argv[i]);
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			continue;
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		}
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		ndir.mode = (dir->mode & ~mask) | (mode & mask);
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		free(dir);
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		if(dirwstat(argv[i], &ndir)==-1){
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			fprint(2, "chmod: can't wstat %s: %r\n", argv[i]);
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			continue;
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		}
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	}
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	exits(0);
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}
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int
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parsemode(char *spec, ulong *pmask, ulong *pmode)
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{
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	ulong mode, mask;
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	int done, op;
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	char *s;
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	s = spec;
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	mask = DMAPPEND | DMEXCL | DMTMP;
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	for(done=0; !done; ){
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		switch(*s){
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		case 'u':
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			mask |= U(DMRWE); break;
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		case 'g':
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			mask |= G(DMRWE); break;
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		case 'o':
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			mask |= O(DMRWE); break;
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		case 'a':
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			mask |= A(DMRWE); break;
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		case 0:
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			return 0;
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		default:
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			done = 1;
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		}
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		if(!done)
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			s++;
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	}
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	if(s == spec)
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		mask |= A(DMRWE);
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	op = *s++;
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	if(op != '+' && op != '-' && op != '=')
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		return 0;
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	mode = 0;
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	for(; *s ; s++){
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		switch(*s){
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		case 'r':
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			mode |= A(DMREAD); break;
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		case 'w':
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			mode |= A(DMWRITE); break;
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		case 'x':
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			mode |= A(DMEXEC); break;
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		case 'a':
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			mode |= DMAPPEND; break;
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		case 'l':
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			mode |= DMEXCL; break;
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		case 't':
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			mode |= DMTMP; break;
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		default:
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			return 0;
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		}
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	}
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	if(*s != 0)
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		return 0;
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	if(op == '+' || op == '-')
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		mask &= mode;
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	if(op == '-')
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		mode = ~mode;
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	*pmask = mask;
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	*pmode = mode;
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	return 1;
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}