tread.c - plan9port - [fork] Plan 9 from user space
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       ---
       tread.c (1278B)
       ---
            1 #include <u.h>
            2 #include <libc.h>
            3 
            4 int        multi;
            5 int        nlines;
            6 char        *status = nil;
            7 
            8 int
            9 line(int fd, char *file)
           10 {
           11         char c;
           12         int m, n, nalloc;
           13         char *buf;
           14 
           15         nalloc = 0;
           16         buf = nil;
           17         for(m=0; ; ){
           18                 n = read(fd, &c, 1);
           19                 if(n < 0){
           20                         fprint(2, "read: error reading %s: %r\n", file);
           21                         exits("read error");
           22                 }
           23                 if(n == 0){
           24                         if(m == 0)
           25                                 status = "eof";
           26                         break;
           27                 }
           28                 if(m == nalloc){
           29                         nalloc += 1024;
           30                         buf = realloc(buf, nalloc);
           31                         if(buf == nil){
           32                                 fprint(2, "read: malloc error: %r\n");
           33                                 exits("malloc");
           34                         }
           35                 }
           36                 buf[m++] = c;
           37                 if(c == '\n')
           38                         break;
           39         }
           40         if(m > 0)
           41                 write(1, buf, m);
           42         free(buf);
           43         return m;
           44 }
           45 
           46 void
           47 lines(int fd, char *file)
           48 {
           49         do{
           50                 if(line(fd, file) == 0)
           51                         break;
           52         }while(multi || --nlines>0);
           53 }
           54 
           55 void
           56 main(int argc, char *argv[])
           57 {
           58         int i, fd;
           59         char *s;
           60 
           61         ARGBEGIN{
           62         case 'm':
           63                 multi = 1;
           64                 break;
           65         case 'n':
           66                 s = ARGF();
           67                 if(s){
           68                         nlines = atoi(s);
           69                         break;
           70                 }
           71                 /* fall through */
           72         default:
           73                 fprint(2, "usage: read [-m] [-n nlines] [files...]\n");
           74                 exits("usage");
           75         }ARGEND
           76 
           77         if(argc == 0)
           78                 lines(0, "<stdin>");
           79         else
           80                 for(i=0; i<argc; i++){
           81                         fd = open(argv[i], OREAD);
           82                         if(fd < 0){
           83                                 fprint(2, "read: can't open %s: %r\n", argv[i]);
           84                                 exits("open");
           85                         }
           86                         lines(fd, argv[i]);
           87                         close(fd);
           88                 }
           89 
           90         exits(status);
           91 }