read: add -c flag to copy bytes instead of lines
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@ -12,7 +12,10 @@ cat, read \- catenate files
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.B -m
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] [
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.B -n
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.I nline
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.I nlines
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] [
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.B -c
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.I nbytes
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] [
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.I file ...
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]
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@ -54,9 +57,21 @@ The
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flag causes it to continue reading and writing multiple lines until end of file;
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.B -n
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causes it to read no more than
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.I nline
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.I nlines
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lines.
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.PP
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With the
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.B -c
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flag,
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.I read
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copies exactly
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.I nbytes
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of characters instead of lines. It is mutually exclusive with
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.B -n
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and
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.B -m
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flag.
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.PP
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.I Read
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always executes a single
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.B write
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@ -3,6 +3,7 @@
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int multi;
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int nlines;
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vlong nchars;
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char *status = nil;
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int
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@ -52,30 +53,61 @@ lines(int fd, char *file)
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}while(multi || --nlines>0);
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}
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void
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chars(int fd, char *file)
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{
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char buf[8*1024];
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vlong m;
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int n;
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for(m = 0; m < nchars; m += n){
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n = sizeof(buf);
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if(n > (nchars - m))
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n = nchars - m;
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if((n = read(fd, buf, n)) < 0){
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fprint(2, "read: error reading %s: %r\n", file);
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exits("read error");
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}
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if(n == 0){
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if(m == 0)
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status = "eof";
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break;
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}
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write(1, buf, n);
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}
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}
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void
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usage(void)
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{
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fprint(2, "usage: read [-m] [-n nlines] [-c nbytes] [files...]\n");
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exits("usage");
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}
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void
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main(int argc, char *argv[])
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{
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void (*proc)(int, char*);
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int i, fd;
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char *s;
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proc = lines;
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ARGBEGIN{
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case 'c':
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nchars = atoll(EARGF(usage()));
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proc = chars;
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break;
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case 'n':
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nlines = atoi(EARGF(usage()));
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break;
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case 'm':
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multi = 1;
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break;
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case 'n':
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s = ARGF();
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if(s){
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nlines = atoi(s);
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break;
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}
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/* fall through */
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default:
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fprint(2, "usage: read [-m] [-n nlines] [files...]\n");
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exits("usage");
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usage();
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}ARGEND
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if(argc == 0)
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lines(0, "<stdin>");
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(*proc)(0, "<stdin>");
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else
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for(i=0; i<argc; i++){
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fd = open(argv[i], OREAD);
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@ -83,7 +115,7 @@ main(int argc, char *argv[])
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fprint(2, "read: can't open %s: %r\n", argv[i]);
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exits("open");
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}
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lines(fd, argv[i]);
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(*proc)(fd, argv[i]);
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close(fd);
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}
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